Isoseismals: Distribution of Apparent Intensity — ContinuedArea of the Santa Cruz Quadrangle of the U. S. Geological SurveyThe distribution of intensity in the area of the Santa Cruz Quadrangle was studied by students of Stanford University, under direction of Prof. J. C. Branner. The contributors to data embodied in this part of the report are Messrs. R. V. Anderson, H. W. Bell, B. Bryan, R. E. Collom, R. Crandall, P. Edwards, H. P. Gage, F. Lane, R. Moran, R. L. Motz, A. F. Rogers, S. Taber, A. F. Taggart, F. W. Turner, and G. A. Waring. Stanford University (J. C. Branner). — Referring to the group of dwellings southeast of the University quadrangle, there were 61 residences on the campus of Stanford University at the time of the earthquake. Out of 140 chimneys on these buildings, 104 were thrown down, or 74 per cent. The plaster was generally badly broken on the first floors of these buildings, and less injured tho generally more or less cracked in the second-floor rooms. At No. 13 Alvarado Row, first floor, several pictures 18 inches across, and hanging by cords 4 feet long, were swung so far that they were left with their faces to the wall. On the corner of Salvatierra and Aguello Streets, a frame building occupied by the Chi Psi Fraternity was so badly wrecked that it had to be abandoned. The injury done this building was due to its having stood upon posts 4 feet high and not well braced; the swaying of the building threw it off these supports. President Jordan's residence, west of the quadrangle, had 3 brick chimneys, all of which were thrown down; the plaster was so badly injured that the first floor, the ceilings, and part of the second floor had to be replastered. This building rested upon a brick foundation about 4 feet high. The Stanford residence, a mile north of the quadrangle, was so badly wrecked that it has since been torn down. The original building was of brick, and wooden additions had been built on the northwest and southeast sides of the brick portion. The additions stood upon wooden uprights 4 feet in length. The southeastern wooden addition was thrown from its supports and fell away from the older brick portion. The brick portion of the structure was badly shattered. In the grounds and parks about the residence there were many marble and bronze statues from 4.5 to 5 feet high, standing on pedestals from 2 to 4 feet high. These were all thrown down, except a few that were very securely bolted to heavy pedestals. There was no uniformity in the directions in which they fell. Between the Stanford residence and the museum, a large 2-story brick winery had the 4 gable ends thrown down. The northwest gable fell into the building, the southeast gable fell outward, while the gables on the northeast and southwest sides fell outward. Mr. Charles G. Lathrop's residence is not on the valley floor, like the other buildings in the immediate vicinity of the University, but stands on a hill of sandstone nearly 300 feet above the level of the bay. Out of the 4 brick chimneys on his house 2 were thrown down; 2 water-tanks 53 feet high (10-foot tanks on 43-foot supports) were not injured, but about two-thirds of the water was thrown from them. Professor Durand's house, south of the quadrangle, is on a hill 160 feet above the bay and stands on the upturned edges of gravel beds that underlie the Santa Clara Valley. Of 3 chimneys, 2 were thrown down, and the plaster was cracked on the ground floor. Of the University buildings proper, some were unhurt while others were completely wrecked. (See plate 102B.) They all stand upon the loose gravelly loam of the Santa ― 256 ―
Clara Valley floor. As a rule, the older the buildings were the better they withstood the shock. Much damage was done by the
throwing down of stone chimneys. The 150-foot stone chimney of the power plant was thrown down, crushing part of the boiler
house and killing a fireman. The double-flued 60-foot chimney of the assay laboratory fell. The large stone chimneys of the
dormitories were broken off at the roof edges and fell into the buildings. At Encina Hall, the men's dormitory, one chimney
fell thru the roof and carried down a tier of rooms into the basement, killing one student. The south ends of the wings of
Encina Hall were so badly cracked that they had to be entirely rebuilt. It was found that the injury done to the ends of the
wings was due to the relation of these particular walls to the roof beams. Excepting the cracking of plaster, Encina Hall
was not otherwise injured, tho it is a 4-story building, with basement and attic.
The chimneys also fell from Roble Hall, the women's dormitory, and did some damage to the roof and upper floors; but the building, which is of concrete, was otherwise unhurt. The Chemistry building had 32 tile-lined stone ventilating chimneys projecting 12 to 16 feet above the roof, besides 2 ordinary stone chimneys; these were all thrown down. The stone tower of the church was shaken to pieces, and in falling destroyed the parts of the roof immediately around the tower. The north gable end of the church was thrown outward into the quadrangle. (Plate 103B.) The top of the memorial arch was broken off down to the upper part of the frieze, and in falling it wrecked adjacent portions of the arcades to the east and west. (Plate 103A.) The parts of the arch left standing were cracked. The 2 smaller arches at the east and west ends of the inner quadrangle were slightly cracked near the top, but they were not seriously damaged. Besides the damages to the church and the memorial arch, the most serious injury to the quadrangle group of buildings was done to the larger structures. The 1-story buildings, especially those that had been standing for several years, were not damaged beyond the occasional cracking of plaster; and even in these cases the injury was found to be directly related to the method of supporting the roofs upon the walls. The statues of the front façade were dislodged and one was thrown down. (Plate 100B.) The 1-story buildings in the outer quadrangle had all been lately put up, and these were somewhat cracked, tho none of them was seriously hurt. The cracks were generally about the ends of the buildings and along the tops of the walls where the roof timbers rested upon them. The higher buildings of the outer quadrangle were more seriously damaged, especially those situated on the corners. These buildings are all three stories and basement. The towers on the inside corners of these buildings were all more or less broken and require rebuilding. The Civil Engineering building — three stories and basement — at the southeast corner of the outer quadrangle had its outer walls badly cracked, especially on the north face, and about the tower at its northwest corner. Inside the plaster was injured more or less all thru the building. The Geology building, at the southwest corner of the outer quadrangle, was the last building of this group to be put up. It was a 3-story structure, and had barely been finished; but it was not yet occupied when the earthquake occurred. Sections of the walls were thrown down from every face of the building. These sections extended from the eaves down to the second floor. The tower at the northeast corner was badly cracked and part of it fell. The plaster was broken on all the vertical walls, both on the outside walls and on the partitions, showing that there was much internal wrenching of the building. The walls of this building will all have to come down and be rebuilt from the foundation. (Plate 102A.) The inner arcades of the quadrangle were not much affected. At one place on the south side of the memorial court, where the arcades are not directly connected with any other building, they were so violently swayed that they seem to have come near falling. They were found to be 7.75 inches out of alinement after the earthquake, and the tops and bases of the supporting stone columns were chipped off. (Plate 105B.) ― 257 ―
The arcade along the south side of the outer quadrangle that was not directly connected with the other buildings was completely wrecked. The arcade in front of the French building on the east side and a corresponding piece in front of the Physics building on the west side of the outer quadrangle were thrown down. South of the business office, parts of the outer arcades fell. This is on the east side of the quadrangle. Parts also fell south of the Mineralogy building, on the west side of the outer quadrangle. (Plate 105A.) The arcades around the memorial court are only partly in direct connection with buildings. The free portions appear to have swayed so far out of the vertical that the bottoms of the stone columns supporting the arches were chipped off, or cracked at their bases. The 2-story woodworking shop of brick, south of the quadrangle, was badly damaged; and the forge building, next to it, also of brick and 1-story, was cracked. The chemical laboratory, a new stone-faced building (two stories, attic and basement), was so badly cracked that most of the walls have to be rebuilt from the foundation. The new gymnasium, a stone-faced brick building, was totally wrecked. (Plate 104B.) It had just been put up, and the inside work was not yet finished. The new library, also a stone-faced brick structure, was completely wrecked except a tower of steel on which its central dome still stands. (Plate 104A.) This building had just been put up, and was not yet finished on the inside when the earthquake occurred. The Museum building consisted of an older central portion built of concrete, and extensive additions of brick had just been completed. The new brick portions of the building were almost all thrown down, but the older concrete part was unhurt. The ornamental stone gateway at the entrance to the university grounds, near Palo Alto, was thrown down. (Plate 101B.) The water-tank at the Faculty Club-house was wrecked and a water-tank in the fields east of Alvarado Row was overthrown. The large covered tanks west of the stock farm, beside the county road, were not thrown down, but much water was split from them. Palo Alto (A. F. Rogers). — The most interesting effects of the earthquake in Palo Alto were those which showed movement of buildings and those which gave evidence of twisting. A number of buildings moved toward the southeast 1 to 6 inches or more. Some buildings were left out of plumb and usually they were inclined to the southeast. In other cases, buildings collapsed and fell toward the southeast. It should be remarked that practically all houses moving to the southeast were those situated on the streets running northwest-southeast. Very few buildings on the avenues (running northeast-southwest) were moved at all. The moved buildings stand approximately at right angles to the fault-line southwest of Stanford University. A change in the direction of the earthquake movement is suggested by the fact that in several cases the chimneys were apparently twisted from their normal positions. The same is true of several houses that collapsed. The twisting was clockwise in some cases and counter-clockwise in others. A remarkable case of twisting was shown in the house at 727 Cowper Street, where picture frames were tilted from the normal positions. Chimneys were mostly knocked down, those that remained standing being for the most part in the centers of the houses. The direction of their fall was apparently accidental. A curious case is that of three 1-story frame houses, exactly alike, at 317, 323, and 329 High Street. The chimney on the house at 329 remained standing, while the chimneys on the other two houses fell.
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Menlo Park (H. P. Gage). — At the Catholic Seminary near Menlo Park, a 4-story brick building, the upper part of many of the walls fell; towers and chimneys also came down; arches were sprung apart, allowing their keystones to drop, catch, and hang. There were many cracks in all the walls which remained standing; the capstones above the windows on the fourth floor fell out. The chapel behind the northeast side wall was thrown in a heap. The 1-story brick buildings back of the large one were little damaged; a wooden tank was uninjured, altho it was on an 80-foot tower like the one in the building which fell. The round power-house chimney (35 feet high) was cracked in the middle and the top broken off. A mile nearer Fairoaks Station, a water-tank only 12 feet high was thrown down. With this one exception all the tanks on this side of the county road appeared to be standing. (F. Lane.) — A water-tank beside the road, passing north of the cemetery 1.5 miles southwest of Menlo Park Station, was thrown down; while one about 0.25 mile nearer the station on the same road was left standing. On the second road west of San Francisquito Creek, and running southwest from Menlo Park Station toward the Alameda de las Pulgas, three large trees growing together had been torn apart, and one about 2.5 feet in diameter had fallen. Water-tanks on the second road west of San Francisquito Creek were not thrown down. On the second parallel road west of the Creek, and leading southwest from Menlo Park and 1 mile from the station, the roof of a large 3-story brick house, which had been recently built, had collapsed, the bricks having been shaken from the walls down to the second floor. The Arcade of the Sacred Heart Convent was thrown down. (Plate 101A.) Fairoaks. — On the road leading southwest from Fairoaks and about a mile southwest of that station, a newly completed 1-story bungalow had entirely collapsed. (S. Taber.) — At a stable near Fairoaks (about a mile southeast of the junction of the Woodside Grade road with the road leading across University Heights) heavy carriages and wagons were moved sidewise 6 inches in a direction N. 37° E., but they did not roll out on their wheels. These carriages were placed on the northwest side of the barn. (H. P. Gage.) — Following the road from Fairoaks toward Cooley's Landing, a house with poor underpinning fell over, also the woodshed near it. An engine mounted on a platform 2 feet from the ground was not upset. People reported new holes formed in the slough near Cooley's Landing, but their statements were not verified. No damage except broken chimneys was noticeable in the vicinity of the Landing, and solidly built houses seemed to be intact. One house on a poor foundation was knocked down; while the barns, tanks, etc., belonging to it were uninjured. (F. Lane.) — South of Menlo Park and east of the Meyer Place on the west side of San Francisquito Creek, a crack about 1.5 inches wide ran for 20 feet along the edge of the county road parallel to and just above the creek, showing a half-inch vertical displacement, the lower side lying next to the creek. This crack appears to be due to the starting of the filled ground of which the road is partly made. The water in the reservoir of the Bear Gulch Company, 3.25 miles west of Stanford University, is reported to have been thrown about 25 feet beyond the dam on the southeast side of the lake. Water-pipes along the road leading from the reservoir toward Menlo Park had been pulled apart. The buildings in the neighborhood of the reservoir are of frame, and no great damage was done to them, except that the brick chimneys were thrown down. Redwood (R. V. Anderson). — The intensity of the earthquake in Redwood City was about IX. Many buildings were partially wrecked and the new court-house was completely ruined. Over 40 houses in the town were moved upon their foundations, and a majority of the houses had the plaster badly cracked. Ninety-four per cent of the chimneys fell, and dishes and similar objects were universally thrown down. Along the two roads leading from Redwood to Portola, out of 23 big public water-tanks 20 were thrown down. ― 260 ―
East of Palo Alto (S. Taber). — On the Embarcadero road, from the railroad crossing at Palo Alto toward the Bay of San Francisco, only about half the brick chimneys had been thrown down. Plaster on first-floor walls cracked, but it was not injured to any extent in the upper stories. Many houses showed little damage to plaster, even on the first floor. The tanks of the Palo Alto Water Company (at 1, map No. 22) had not been thrown over, but the frame (100 feet high) had slipt on the concrete foundation a maximum distance of about 0.5 inch in a direction N. 87° E. The water is reported to have slopt out of the reservoir on the east side. A water-tank about 0.5 mile nearer the bay (at 2, map No. 22) was standing, as was a brick chimney near it. Damage to houses in this section was directly due to high brick chimneys; plaster was sometimes scarcely cracked, even on the first floor of houses thus damaged. Mayfield to Guth Landing (R. L. Motz). — In the town of Mayfield most of the houses are small, 1-story buildings resting on wooden foundations, and many of the chimneys were of terra cotta and wired to the roofts. Out of a total of 258 chimneys 183 fell — about 70 per cent. A few brick buildings were badly cracked, and the fire-walls were all thrown off. The plaster in the small buildings was somewhat cracked, while in the larger buildings the damage done to plaster was more marked. The concrete bridge over Madera Creek, on the county road 0.5 mile southeast of Mayfield, was not cracked. A half mile further southeast along the road, 2 water-tanks and 3 chimneys (2 brick and 1 cobble-stones and lately built) were standing. A short distance nearer Mountain View Landing there were fallen or damaged chimneys (at 4 and 5, map No. 22). At Guth Landing a large brick warehouse facing N. 87° E. had its sides cracked, lost a few bricks at the top, and had the upper part of its east and west ends knocked out. From Guth Landing southward along the road into Mountain View, the effects were uniform; chimneys were down with two exceptions, there was little or no damage to plaster, and the flow from bored wells had increased. In one case a wind-mill (at 6, map No. 22), which had been in use for years to pump water from the well, was no longer found necessary, but the artesian water was muddy. Mountain View (H. P. Gage). — On the county road between Mayfield and Mountain View, concrete bridges were uninjured, water-tanks were left standing, and the smaller or more solidly built chimneys uninjured. (R. L. Motz.) — In the new town of Mountain View, built mostly in the vicinity of the railway station, 6 brick structures, including the Pacific Press and the cannery buildings, were seriously injured. Out of 271 chimneys, 206, or 76 per cent, fell; out of 46 large water-tanks 20, or 43 per cent, fell. In the Mountain View Cemetery there were 26 large monuments; of these 11 fell and 7 were shifted, while 13 slab headstones out of 27 were thrown down. In the village of Old Mountain View 75 per cent of the chimneys (31 out of 41) fell, and 33⅓ per cent of the water-tanks (3 out of 9) fell. (H. P. Gage.) — On the road leading southwest toward San Antonio Creek from the town of Mountain View, the houses showed no uniform damage. At one place south of the county road and two miles west of the Mountain View Station, the water-tank swayed and threw out several barrels of water during the shock, yet the plaster in the house was unhurt and only a few dishes were broken. At the next house, the chimney fell. At the Weeks poultry ranch 2 chimneys fell, dishes were broken and plaster was cracked; but the water-tank was uninjured. Two and a half miles southwest of Mountain View Station, beside the road running up San Antonio Creek, a water-tank was so badly wrenched that it had to be braced to keep it from falling; another tank, on a side hill west of San Antonio Creek, had collapsed. The house near the latter, in course of construction, lost an outside chimney. Following the road up San Antonio Creek on its southeast side, another house between the road and the creek had one chimney cracked and another thrown down; plaster had ― 261 ―
fallen in the second story, and sewer and underground pipes were broken. Much damage was also done to the houses on the hill
southwest of where this road crosses San Antonio Creek. In one of these 3-story houses, the plaster was partly off the first
floor walls, and windows were broken. The second house was so shaken that it shifted several inches upon its foundations.
A 1-story cottage close by was little damaged; and in the pumping shed, bottles, cans, etc., standing on a narrow shelf did
not even fall down. The chimneys were thrown down on the ranch house at Hidden Villa, two miles northwest of Black Mountain
Triangulation Station, but there was no great damage otherwise. Big blocks of rock are said to have been shaken loose from
the mountain and to have rolled down the slopes. One of these rolled into the chicken-house, and others broke the water-pipes
at several places farther up the gorge.
On the road running southwest from Mountain View Station toward San Antonio Creek and 1.75 miles southwest of the station, a water-tank 8 feet high was thrown down. In the village of Mountain View, 0.5 mile southwest of the railway station, one chimney on a small house, and projecting 5 feet above the roof, was left standing; while another chimney on the same house was thrown down. On the road leading north from Mountain View, and 0.25 mile from the station, one chimney fell; but another, 1 × 2 × 3 feet was standing. The latter was braced with iron bolts, however. The plaster in the house was cracked, though not very badly, and the foundations were unhurt. At the Ynigo ranch, 3 miles northeast of Mountain View Station, the house is large and old. Here the chimneys fell, one going down through the roof. The plaster was only slightly cracked. Frail sheds and water-tanks 20 feet high on light supports were not thrown down, and plumbing in the house was apparently undisturbed. There was an artesian well at this place which had, before the shock, flowed only slightly or not at all, and a wind-mill was used to raise the water. After the shock, it was found that the casing had been shoved up 2 feet, damaging the pump. The flow of water was increased and black sand was brought up. Another well at this ranch was unaffected. At Jagel Landing there was but little damage. One chimney was unhurt, and another was slightly twisted. The concrete bridges over Permanente and San Francisquito Creeks showed no new cracks. In the low lands northeast of Mountain View, all the chimneys except one at the Mascot Gun Club preserve had been thrown down, and water-tanks had fallen except where they had been especially well braced. The same was true in the vicinity of Sunnyvale. Between Sunnyvale and Lawrence a brick winery was destroyed, and a tank and wind-mill were thrown to the ground. On the second east-and-west road directly south of Sunnyvale, for a short distance toward Stevens Creek, a few chimneys were left standing; but the damage was generally uniform as reported above. (F. Lane.)—A 3-story brick wine distillery in the northeast corner of the San Antonio grant, 3.5 miles south of Mountain View Station, was totally destroyed by the shock. This building was on the side of a hill. A 3-story frame house near it lost its chimney and was tipt to one side. A half-mile south of the winery, a water-tank beside the road had been destroyed. At the southeast corner of the same grant, a 2-story frame house (Sellinger's) was thrown from its 4-foot brick foundation and badly damaged. The road in front of the house was cracked, but probably on account of the steep slope below the road. South of the house, across Stevens Creek, there was a landslide 100 feet in width on the steep face of a bluff. (S. Taber.)—The concrete bridge over Stevens Creek on the county road below Mountain View was not cracked, but at the brick yard, at the junction of the San Jose road with the road to Jagel Landing, a high chimney and a pile of brick had fallen over. Saratoga to Congress Springs (F. Lane).—At Saratoga some chimneys were knocked off, but among those standing was a high chimney built on the side of a 1-story house. A wind-mill with a large tank had not been injured and no other damage was apparent. ― 262 ―
On the Azule Springs road, all the 1-story buildings appeared to be in good condition, and few effects of the shock were noticeable. Near the place where five roads fork, one mile north of Azule Springs on the road running southeast from the forks, there was a 6-foot drop on the road caused by a section sinking in a solid piece on a long slope, without much disturbance in its vicinity. At the cross-roads halfway between Saratoga and West Side, the Lincoln school-house, on wooden supports, was thrown from its foundation and badly damaged. The tank behind the school-house was standing, as were all the tanks on the road from Saratoga to West Side except the one nearest the latter village. Only one more effect of the shock was noted in this vicinity; namely, the bridge over Stevens Creek, on the road running due east and west from West Side, was rendered unsafe for horses by being shoved a foot out of place. On the Stevens Creek road, just after leaving the Saratoga road, one house near the junction of the two roads was shaken and dishes were broken, but the brick chimney was intact. Near the house a crack 2 inches wide showed a downthrow of 2 inches on the west side. A vacant house at the next turn, 0.5 mile southeast of Stevens Creek, had lost its chimney and leaned with the slope of the hill. Near this house a large area of ground, extending for 150 feet, had been torn up in a direction of N. 3° W., and a slide formed which almost blocked the road. At the Borger place on the Stevens Creek road, the chimney was shaken down; the house, which stands on a high but well-built stone foundation, was not damaged otherwise. Wine was spilt in the cellar by the force of the shock. Further northwest along this road other disturbances were noted with increasing frequency; small cracks crost the road due north and south. On the northeast side of the creek, 0.25 mile south of the place where a road turns northeast from the Stevens Creek road to go up Monte Bello ridge, there was a large landslide about 0.5 mile long and terraced from the top of the mountain. The short road which runs northwest along Stevens Creek for a couple of miles beyond the junction with the cross-road which connects with the Monte Bello ridge showed an exposure of serpentine with cracks running along it N. 3° W. The cracks at the widest point measured about one foot. In the serpentine area the ground was badly broken up, and in one place it was covered with 3 feet of water. (Observation made April 22-23.) Following the road northwest beyond the terminus shown in the map, many cracks were seen, due to big landslides. Fallen trees have rendered the road impassable; boulders and dead trees still fell occasionally; even while the observer was there a large tree fell not 10 feet from him, loosening rocks and soil. Just south of the two houses near the southern end of the cross-road leading toward the Monte Bello road from the Stevens Creek road, a break ran due east and west; it was 2 inches wide with a downthrow of 0.25 inch on the west side. Only dishes were broken in the house, a 1-story frame structure without chimneys, tho it stands above the big slide which was just mentioned. Another crack 4 inches wide was found in the road above the house. The village of Congress Springs had not been shaken very badly. All water-pipes and tanks were intact and very little timber seemed to have fallen. The car tracks on the curve near the path to the spring had been thrown over toward the bank for about 20 feet of the curve, a 4-inch displacement resulting. The 2-story stone building of the Saratoga Wine Company was partially thrown down, and the side nearest the road had to be propt up to keep it from falling. At this point several cracks were noticed in the loose alluvial material of the road, almost at right angles to each other. Stanford University to Portola and Woodside (S. Taber).—Going southwest from Stanford University along the road leading up San Francisquito Creek (at 8, map No. 22), on the banks of the creek many dead limbs were broken from trees, and a dead oak ― 263 ―
2 feet in diameter was broken off about 20 feet from the ground. But little damage was done at a house a short distance farther
west. On the north side of the creek (at 9, map No. 22), the 12-inch cast-iron pipe of the Stanford University water-main,
buried about 3 feet deep, was cracked, allowing the water to spurt 20 feet into the air.
Beside the road just west of Searsville reservoir, a living white oak 6 feet in diameter was uprooted by the jerk of the earthquake shock. (Plate 106A.) At the Searsville dam the waste way is 45 feet wide. The water running over the spillway was 4 inches deep before the earthquake, but afterward it increased to 5 inches; more water was also noticed in the creek that empties into the lake. The Preston residence, about 0.5 mile south of Searsville Lake, lost its chimneys. Along the road leading from Searsville Lake southeast thru Portola, the water-tanks were all thrown down, except one near the junction of the Portola road with the Alpine road. The bridge at the north end of the village of Portola had the ends thrust together so that the planks forming its floor were thrown out of place. In Portola, brick chimneys were all down and water-pipes were broken. The Portola store was thrown off its foundation. The Catholic Church in the village is a frame building that stood upon an underpinning of posts about 3 feet high. This building was thrown bodily about 2 feet toward the north, apparently thrust over by the underpinning when it gave way. The Portola school-house was also thrown from its foundation, which was about 3 feet above the ground. Two small dwelling-houses southeast of the school-house and on the south side of the road were thrown from their foundations. Following the Portola road from Portola toward Woodside, the houses showed considerable damage, with chimneys down. The water-tank at the fork of the road in front of Mr. Preston's house was thrown down, and the big tank at the fork of the road, at the site of the old village of Searsville, was also thrown down. The white oaks in the field north of the road had also many large branches broken off by the shock. A shanty between the 2 bridges (at 11, map No. 22) was down flat; and in a few cases the underpinning of houses had given way, the houses having settled in consequence. Small trees were overturned and fences broken. A large live oak had its top broken off about 20 feet from the ground (at 12, map No. 22); at the place of fracture the tree is about 3 feet in diameter. Taking the western road past Newman's, which is at the place where this road crosses Bear Creek, from Searsville Lake to Woodside, two especially well-built water-tanks beside the road, tho well shaken on their foundations, did not fall. On the south side of the road, about 0.25 mile southeast of Mr. Folger's, a large live oak was torn up by the roots (plate 106B), while several eucalyptus trees had branches jerked off. A strongly built 1-story house just below (13, map No. 22), and within 400 feet of the fault-line, lost all of its chimneys, but the plaster was only slightly cracked. Beds and other furniture in the house were jerked in directions parallel to the fault-line. A small bed standing in the northwest corner of a room was not moved, but a larger bed near the center of the same room was moved several feet. A water-tank a short distance northwest of the house, new and strongly built, about 15 feet above the ground, had nearly all of the water spilt out of it. An eye-witness says that the water was thrown high up on the northwest and southeast sides. The water-pipe running from the house to the pump was bent in a curve toward the northwest, and where it entered the pump-house, the boards were broken on the southeast side of the pipe. The other pipe (also 4 inches in diameter) had the threads stript off at a joint, and the ends of the pipe pulled apart for a distance of 2.5 to 3 inches. The pipe was new and buried a few inches below the surface of the ground. A large oak tree standing 200 feet or so from the house had large limbs broken off by the shock. At the Folger place, between Newman's and Portola, the chimneys were all thrown down. ― 264 ―
On the west side of Bear Creek and north of the road along the foot of the mountain near Woodside, a 1-story sandstone house had its south wall thrown down, and was otherwise badly damaged. About 50 feet of stone wall, laid with mortar, along the side of the road, 3 feet high and 1.5 feet wide, was thrown down. A tank at the cross-roads in Woodside was left standing. The upper part of a brick winery 1½ stories high (at 26, map No. 22) was demolished, the roof being split down the middle and smashed to pieces. A house 1½ stories high (at 14, map No. 22) was thrown toward the southeast, the underpinning giving way in front. The house was badly damaged. Water in a large tank near the house spilt out on the southeast and northwest sides. At the very end of the short, crooked road mapped as running northwest from the village of Woodside, there was a well-built 1-story frame house, of which the brick chimney had been thrown down; the plaster of the house was only slightly cracked. Near this a large water-tank was thrown over; another remained standing but had the shingles knocked off the roof on the northwest side by the force of the water dashing up against it. The old adobe house at the cross-roads in the village of Woodside was thrown down, the posts and supports left standing leaned at a considerable angle toward the northwest. A large frame house (Mr. Josselyn's residence), north of the road and close to West Union Creek, was demolished; while another on the opposite side of the road, and just south of the bridge, was not badly damaged. The concrete bridge over West Union Creek, 1 mile south of the point (14, map No. 22), showed a few small cracks. From this point on up King's Mountain road, as far as the summit, there were no cracks nor landslides. Page Mill and Alpine roads (S. Taber). — All brick chimneys along the upper part of this road were thrown down. At the Clarita Winery crockery was broken and milk spilt from pans. On the road from Clarita Vineyard to the Allen place (at 18, map. No. 22), several small cracks 0.25 to 0.5 inch across ran east and west; numerous cracks intersected (near 18, map No. 22) in various directions, while some large ones running parallel to the contour lines were probably due to earth slipping. Judge Allen's in the valley, and several smaller houses, were thrown from their foundations and otherwise badly damaged. Following the Alpine road up Corde Madera Creek, cracks were common on the outside or filled portion of the road, and these were generally parallel with the embankment. The steep southern slope of the ridge just north of the Alpine road, along its lower course, was favorable to landslips. At many places huge masses of rock had been thrown down from these steep bluffs into the road, completely blocking it up. On the south side of the creek the slopes were not favorable to landslips, but there were several of them; and at one point, about a mile from the summit of the ridge where this road enters the Page Mill road, one slide carried away the entire roadbed for a distance of about 300 feet. (H. P. Gage.)—Following the Page Mill road westward from Black Mountain toward Langley Hill, a 1,000 gallon tank was undisturbed, but 3 live-oaks near by were uprooted, one of them being a large tree with a 12-foot base. These trees were in a rather dry soil, yet none of a grove of trees growing in moist soil was overturned. Farther west up the road which loops toward Langley Hill, a big crack running east and west, caused by a slide, showed a drop of 8 inches on the north side; and from here on down to the Alpine road the road was badly cut up with slides, but was not impassable. On the steep grade of Langley Hill a slide had moved 30 feet. At the ranch houses there was little damage done by the shaking save sometimes a fallen chimney or a few broken dishes. At one ranch the people reported that cows were much frightened during the shock. (F. Lane.)—Along the ridge road southwest of Stevens Creek, separating Santa Clara and Santa Cruz Counties, there were some cracks due to landslides. Sandstone blocks, some of them 6 feet in diameter, had rolled down the hills toward the creek. People at the houses along this road stated that the shaking had been severe, with loss of a few ― 265 ―
chimneys but very little destruction otherwise. No evidence of cracks could be found upon the side road. At a house situated
at the junction of four roads about 3 miles west of Congress Springs, no damage was reported, tho the inhabitants were up
at the beginning of the shake and say that it was accompanied by considerable rumbling and that the shocks which followed
were preceded by a sound like a blast. [1]
King's Mountain down Purisima Creek (S. Taber). — At King's Mountain House, brick chimneys were knocked down and some dishes were broken, but no damage was done to the house. Cream was spilt from the milk pans on the southwest side. On the Cahill Ridge road leading northwest from King's along the crest of the ridge, little damage was noticeable. An old woodshed was thrown down (at 21, map No. 22), and about a mile farther on the top was broken from a large redwood tree about 75 or 100 feet from the ground (at 22, map No. 22). Following the trail from King's Mountain House down Purisima Creek, a large slide on the northeast side of the creek had filled the road to a width of about 100 feet (at 23, map No. 22). The buildings at Hatch's Mill, just below (24, map No. 22) were not damaged, but a little farther down several cracks were found, one 8 inches wide and running S. 23° E. On the northeast side of the creek, just below Borden's Mill, a big slide had dammed the creek to a depth of 25 or 30 feet (at 25, map No. 22). The slide was between 0.25 and 0.5 mile long. The buildings at the mill showed no damage, but a bridge just above the mill was crusht by a slide from the south side of the creek. Bear Creek (H. P. Gage). — Between Redwood City and Woodside, all of the public water-tanks were thrown down or had to be rebuilt. On the Bear Creek road, southwest of Woodside, there were many cracks caused by landslips down steep banks. The tops of 2 partly decayed trees, one a redwood and the other a spruce, had been broken off where the diameter was 2 feet. Near where the first trail branches to the right from this road, an old oven built of clay and stone, 4 feet high, was cracked, and an old barn was badly damaged. At the point where the road itself becomes a trail there is a log cabin, probably used as a summer camp. This cabin was locked and had apparently remained undisturbed since the earthquake. The floor is about 6 feet above the level of the ground. Table, benches, chairs, and all the bottles and utensils, except a coffee pot, were overturned. The table was solidly built and measured 4 by 8 feet. About a mile east of this cabin, at the end of another trail, was a 1-story frame house; a bed on the first floor was moved by the shock 8 feet to the middle of the room, tables and chairs were displaced, and dishes were broken. A house and dairy between this place and the road were moved on their foundations, and water was spilt out of pails from northeast to southwest. Tops of spruce trees were broken by the shock. Four miles farther southwest, along the trail toward the San Gregorio road, people reported that all the stoves on the first floor of their houses were overturned during the earthquake, with the exception of a kitchen range which was twisted around 6 inches. Their dishes were also broken. Just south of the junction of this trail with the San Gregorio road, a 2-story house had been shifted on its underpinning and some plaster was broken. A watertank 20 feet high fell at this point. Half Moon Bay, Purisima and San Gregorio (S. Taber). — Following the road along Pilarcitos Creek toward Half Moon Bay, many cracks and slides were found on the ocean side of the ridge, but few on the east side. All of these seemed due to slipping of the earth. At one place there had been such a large slide that big blocks of sandstone had fallen down into the road. Here and there along the road big cracks had opened, parallel with the road and the creek where the slope is very steep, and promising to make the road impassable by landslides, should a heavy rain come. ― 266 ―
Just north of the bridge over Pilarcitos Creek, north of the town of Half Moon Bay, an adobe house west of the road was thrown down by the earthquake, killing 3 people (at 30, map No. 22). The concrete bridge was badly cracked, as were the approaches at both ends. Just south of the bridge, several small cracks in the low ground west of the road permitted water to spout up, bringing sand with it. In the town of Half Moon Bay many buildings were badly damaged, some old frame houses and the brick bank building being flat, while the upper half of a 2-story brick structure was demolished. The Mosconi Hotel, a 2-story frame building, had plaster shaken from the side walls of the first floor only, while the ceilings of these rooms were not cracked. In Half Moon Bay it was reported that there was no evidence of any change of level along the coast. The streams on the west side of the mountains were said to have doubled in volume. The road along the coast from Half Moon Bay to San Gregorio showed comparatively few traces of the earthquake. The concrete bridge over Cañada Verde (at 31, map No. 22) was slightly cracked, and 0.5 mile farther south a water-tank lay flat across the road. At Purisima the chimneys were all down, and crockery was broken. The intensity of the shock was apparently less at Purisima than at Half Moon Bay. According to various reports, a crack east of the road below Purisima, due to a landslip, extended for about 1,000 feet nearly north and south; and an earthslide on the side of a hill a mile or more farther south was about 100 yards long and 80 feet across. At San Gregorio very little damage was done. The hotel lost only a little plaster and a few dishes. Turning eastward on the road along San Gregorio Creek, traces were found of increasing intensity. A mile from the town of San Gregorio, a water-tank 20 feet high was still standing, while a couple of miles farther east the creek was dammed up to a depth of 6 feet by a slide from its southeast bank (at 32, map No. 22), and all chimneys were down. Miss L. E. Bell reports that near Bellville a small alkali flat was raised about 3 feet. There was a landslide into the road for a distance of 300 feet, the height of the slide being 100 feet (34, map No. 22). Chimneys and tanks all thru the valley were thrown down. (G. A. Waring.) — Of the 2 stores at San Gregorio, the one in the bottom-land suffered most, nearly all the shelf goods being thrown down. Cracks from 12 to 18 inches wide appeared in the cultivated bottom-land, and a water-tank was shifted on its platform 8 inches northward. In the Lobitos saloon a slot machine was hurled to the floor, and nearly all the bottles on a shelf running east and west were thrown off. Small cracks appeared in the ground at Lobitos, and a small slide occurred in the road 0.25 mile up the stream. La Honda (H. P. Gage). — The inhabitants say that after the shock the creek rose about 4 inches and became muddy. At the hotel, plaster fell from first floor walls; the rest were little damaged. The plaster had already been cracked, however, by raising the house. Lamps were all shaken off the tables, and all the chimneys were down. Water spilt from the horse-trough in a northeast-southwest direction. Near the Weeks ranch house, between La Honda and the summit of the ridge on the road leading to Redwood, an inconspicuous crack was noticed running east. It was about 2 inches wide, with no vertical movement evident. The north side of the crack, however, had moved fully 3 feet eastward. The crack simply marks a big slide which has been slipping for years, and which descended 3 feet during the earthquake. The Weeks house, a strongly-built frame structure, 2½ stories high, was badly damaged. A large outside chimney fell thru the roof to the first floor, and the plaster was fairly stript from the lower rooms and somewhat cracked upstairs. The sliding doors downstairs were shaken off their tracks, several windows were broken, the front door was cracked, and many of the door jambs were broken. The heavily built barn near the house was ― 267 ―
badly strained. The water in the reservoir was spilt from northeast to southwest. In an old house near the summit the stove
was not moved at all, but the chimney built 40 years ago fell.
(S. Taber.) — For some distance on the west side of the summit sandstone blocks had been cracked off and scattered across the road. From the summit of the ridge to the Portola Valley, the only effects noted were the wreck of a ramshackle old barn and a 3-inch crack across the road (at 36, map No. 22), probably due to settling. Congress Springs to Boulder Creek (B. Bryan). — From Congress Springs, following the road that passes along the valley, about a mile east of the Castle Rock Ridge, in a southeasterly direction toward the reservoir of the San Jose Water Company, evidences were found that the earthquake had an intensity of over IX. The walls of a stone barn had been thrown down, 1,000-gallon wine-tanks in a cellar had been shifted, and people in the houses were thrown down while trying to get outdoors at the time of the shock. In a house close by, at the south end of the dam, the first floor plaster fell. Poorly built foundations fell. Southeast of the reservoir the chimneys and water-tanks were down. Two water-tanks at and near the bend of the road (at 37, map No. 22), were standing, but 0.5 mile northwest of this place a water-tank had fallen. The water in the reservoir (at 38, map No. 22) had overflowed the 3-foot banks, but the water-tanks were standing. A short distance down the road, to the northeast of the reservoir, another tank was standing. A house 0.75 mile east of this reservoir was badly shaken, with loss of plaster and chimney. In the section a mile east of the fault-line (at 39, map No. 22) the shock was weaker. All the chimneys on cottages were standing as far as could be seen, as well as all the water-tanks. The bridges 0.5 mile southeast of the reservoir were considerably shaken. Cracks seemingly continuous in the direction of the fault-line ran thru the area 0.75 mile east of the fault-line. Two-story frame houses along the fault line 1 mile southeast of the reservoir mentioned were so damaged within that people were living outdoors; yet the shake had not broken a 6-inch flag pole on a 2-story frame house. A large redwood tree had been shaken down (near 40, map No. 22); the house near it had its chimney fractured down to the fireplace, and the stove and piano were thrown across the room. The water-pipes here were badly displaced and broken. The intensity was greatly diminished, however, near 41, map No. 22; chimneys did not fall, tho fractured; clocks were stopt; little rock was thrown down from a vertical outside wall 15 feet high. On Deer Creek a large landslide started from near Grizzly Rock and slid westward, but changed its direction 60° or more farther down toward the creek. The mill in the creek bottom below the slide was partly buried, and one man was killed. It is 500 feet from the mill in the gulch to the top, at the point where the slide started. The slide covered about 25 acres of ground, and destroyed a lot of virgin timber from 3 to 10 feet in diameter. The slide material, which is 300 feet deep, is composed of soil, clay, and shale. The shock could not have been very strong at 42, map No. 22. The houses stand on posts 10 to 15 feet high, but were not moved noticeably. Furniture facing most nearly north and south was thrown down, but not when facing in other directions. The inhabitants were badly frightened and ran outdoors without waiting to dress. On Bear Creek (at 43, map No. 22) a smaller slide had moved a few hundred feet, buried a hut, and killed one man. According to reports of men in this region, only a minute elapsed after the beginning of the earthquake before the slide was over. Down in the valley no cracks or other evidence of violent disturbance could be seen. Farther southwest down Bear Creek, about 1.5 miles from the village of Boulder Creek, were evidences of a less severe shock. A chimney on a 1-story house did not fall, tho the furniture in the house was thrown down. Trees were violently shaken. A mile northeast of Boulder Creek a chimney on a 2-story house was down, but no buildings were moved or broken. ― 268 ―
In the town of Boulder Creek, all chimneys were down except those on some 1-story cottages; these were cracked, however. People generally ran out-of-doors, but were not as a rule very badly frightened; some even stayed inside until they had drest. Waterpipes were not broken, but some plaster had fallen, and plaster was cracked everywhere. Mr. Bloom, owner of a sawmill at the edge of the Big Basin, reports that the shock was less severe in the Big Basin region than at Boulder Creek; that there were no landslides on the road between the two places; and that, tho he had been nearly to the summit on the day of the earthquake, he had seen only one crack where the earth had started to slide. (R. Collom.) — At Boulder Creek, on the east side of the stream, a small hill of about 150 feet elevation rises rather abruptly. Its sides are thickly covered with small trees and brush. Near the top, a large portion of the surface soil had been shaken loose, and had slid to the level of the creek, carrying trees with it. At Ben Lomond no fissures nor other such evidences of the earthquake were to be seen. Inquiry showed this condition to continue in the country about the town. Broken chimneys were the only evidence. The inhabitants of Ben Lomond report several slight shocks during the night of April 21-22, 1906. (B. Bryan.) — Going north from the village of Boulder Creek along the San Lorenzo River, only small wooden houses were seen, all with chimneys standing. There were few evidences of the force of the shock, except fallen redwood trees. Three dead redwoods had been snapt off from 30 to 50 feet above the ground; and farther on two more were noticed, one having broken and the other having been uprooted. A man who was at the sawmill, 8 miles north of Boulder Creek, at the time of the earthquake, stated that a few trees were torn up by the roots. Cordwood had been thrown down in several instances along here. A small landslide had moved across the road (at 44, map No. 22), which 20 men spent one and a half days clearing away. In the gulch the tops of a number of redwood trees had been broken off from 50 to 100 feet from the ground, the diameters at the point of fracture measuring from 10 to 14 inches. Up the road to the summit of Castle Rock Ridge no slides nor cracks were observed. On Boulder Creek, coming southeast down the China Grade, the shock was strong, but apparently not so severe as along the San Lorenzo River. The people were badly frightened by the shaking, however. One man reported that no redwood trees fell and that only a few dead limbs were broken off. Near the junction of the first road leading from Boulder Creek into the Big Basin, an old landslide which covered about 2 or 3 acres, dating back to the previous winter, had been widened by the shock and its direction had changed. Only a couple of hundred yards farther down the road, some stacks of smooth split redwood logs (cordwood size) had not been shaken down. A small earthslide had started (at 45, map No. 22), and a crack, perhaps due to the same slide, was noticed. For the next mile or so southeast, there was a considerable amount of cordwood along the road, none of which was disarranged by the shock; and no trees nor dead limbs had fallen. In the houses between this place (45, map No. 22) and the sawmill (at 46, map No. 22), the evidences of damage were more serious. At this first place visited no damage was done; people were awakened but did not get up; no trees nor limbs had fallen. At the next place, 1 mile southeast, people ran from the house during the shake and attempted to remove a sick man. Small objects were thrown down and a pendulum clock was stopt. At the house just southeast of the mill, the inside furniture was overturned, the stove moved, and the terra-cotta chimney split and fell; while branches were broken from redwood trees near the house. At the mill the same effects were noted, and others as well; tops of live trees, from 6 to 8 inches in diameter at the fracture, were broken off. From the point (46, map No. 22) down to the road leading to Bloom's Mill, 1 mile south of the point (45, map No. 22), the intensity seemed to have been less. A water-tank beside the road was quite unhurt; houses were ― 269 ―
not badly shaken; and only small objects — cooking utensils, etc. — were thrown down. At an old mill 2 miles southwest, however,
a clock had been thrown upon the floor and broken at 5h 11m A.M. Half of the piled lumber had been disarranged, and the watertank, built on a frame 15 feet high, was shaken so that
it fell the next Monday night.
Ben Lomond Mountain to the Coast (B. Bryan). — At the junction of the Ben Lomond Mountain road (47, map No. 22), the house was empty, but there was no noticeable disturbance in the sheds or neighboring trees, tho a few hundred yards south a few dead limbs had been recently broken from the redwoods and one or two dead trees had fallen. Some other trees were so loosened at their roots that they have fallen since the earthquake. At the Ben Lomond Wine Company, a place 2 miles southeast of the junction of the roads (at 47, map No. 22), a well-built cottage had 2 tall chimneys still standing. People did not leave the house during the earthquake. Leaving the Boulder Creek road, and crossing Ben Lomond Mountain by the Eagle Rock road, the damage appears to consist largely of fallen chimneys. Small objects, such as fruit jars, china, etc., were thrown down, but only from shelves against north and south walls. People left their houses, but were not much alarmed. No evidences of a violent shaking were to be found on the trail following southwest down Big Creek, either in trees or buildings, except where a small, half-decayed shack had been thrown out of plumb and a set of shelves overturned in another cabin. A table near these shelves was unmoved, and the bottles on top of it were standing. At the dam on Big Creek (at 48, map No. 22), no harm had been done, nor was any damage visible in 3 old shacks just below the dam. A half mile from this point cracks caused by slides were noticed on a very steep bank. Slight damage was done to the flume (at 49, map No. 22), which 3 men repaired in half a day. A few objects were thrown down in dwellings hereabouts. Near the junction of Scott and Big Creeks, a light terra-cotta chimney did not fall, but milk was spilt from pans at this place. (H. W. Bell.) — At a house 1 mile southeast of the junction of the east and west forks of Waddell's Creek, a brick chimney was thrown down. Near a deserted mill at the northend of Ben Lomond Mountain, a small landslide had carried trees and brush down to the creek, and tall trees had fallen along the road. At a new mill a short distance from the old one, about a mile northwest of Eagle Rock, it was reported that the shock was distinctly felt, but no damage was done. Dishes even stayed on the shelves. A steep bank beside the road showed small cracks, which could apparently have been easily made in the loose soil. (G. A. Waring.) — At Swanton it was reported that a distinct noise, as of a team crossing a bridge to the northwest, had been heard preceding each shock. Dishes on a shelf running northeast and southwest were thrown off, while those on a shelf standing at right angles to these were unhurt. (B. Bryan.) — At the school-house (50, map No. 22) the globes were overturned by the shock. The teacher said that she had heard from the people at the end of the trail just above, leading northwest toward Swanton, that the shaking had overturned only a few glasses, and that their pendulum clock did not even stop. At the next place, 0.5 mile southeast of the school-house, no damage was done, and the inhabitants were not disturbed enough to run outdoors. In the little settlement at El Jarro Point, the shock was so light that a small chimney with a terra-cotta top, making a height of 7 feet above the roof, did not fall; nor were similar terra-cotta chimneys on 2-story buildings thrown down, tho projecting from 3 to 4 feet. Glasses and bottles remained on the shelves in a bar-room. At the lime-kilns (51, map No. 22) the shock had apparently been more severe, for tho no cracks were found in the kilns themselves, people ran from houses, small objects were thrown to the floor, and piles of cordwood were overturned. ― 270 ―
(G. A. Waring.) — At the San Vicente lime-quarry, the intensity was found to have been considerably higher in the bottom of the canyon. A cow in the yard could not keep her feet, men could not walk to the door of the cook-house, and milk and water were nearly all thrown from the pans and kettles. Little or no damage was done to the buildings or furnaces, and cordwood on the steep slopes was not thrown down. At Coast there was little sign of destruction by the earthquake, and nothing could be learned. At Bonnie Doon, tho the shock was appreciable, no clocks were reported stopt and nothing was thrown from shelves. (B. Bryan.) — On the road thru Bonnie Doon the shock was uniformly light; chimneys were unharmed, plaster was intact, clocks did not stop, and even the milk had not spilt from the pans. People did not run outdoors. A top-heavy and rickety pigeon-house did not fall over, tho shaken considerably. Down Laguna Creek to Coast, and up the trail east of Coja Creek to the asphalt beds, similar effects were noted. Near the latter spot, however, the shock appeared to have been somewhat stronger; small objects had fallen, milk spilt, and even one chimney was thrown down, while people were frightened enough to get out of the buildings. From the asphalt beds as far east as the point 52, map No. 22, the observer found no one to question; but the shake had been so moderate as to leave no visible signs except where some cordwood had broken its end-stakes and rolled down at the ends. At the houses just south of this point, chimneys and plaster of 2-story structures were not damaged; only lamp-chimneys and such articles fell and broke. It was reported that at one house in the valley fruit-cans had been thrown from shelves. (R. Collom.) — At the Wilder dairy, on the Santa Cruz-Pescadero road, 2 miles west of Santa Cruz near Meder Creek, the damage done by the shock was in the form of broken chimneys and cracked plaster in the houses. On the road 0.5 mile west of the dairy, the force of the shock broke an 8-inch water main. A general examination of the country along the coast, as opened up by the Pescadero stage road, shows the damage in these parts to be confined mostly to broken chimneys and cracked plaster in the houses. Only in the case of buildings with very poor foundations was any of the superstructure destroyed. (G. A. Waring.) — At Wilder's dairy it was said that the shock seemed to come southward down the gulch, preceded by a rumbling from the same direction. Other places on the terrace-land near the shore west of Santa Cruz were not so badly shaken. Santa Cruz (B. Bryan). — Entering the city of Santa Cruz from the west, the first chimneys down were only about 0.5 mile from the San Lorenzo River, increasing in number as one came into the town; yet many of the better-built chimneys, even on 2-story and 3-story buildings, were not thrown down. In the eastern part of Santa Cruz, some chimneys on both 1-story and 2-story houses fell, and some stood. In some cases plaster was cracked, but in no case where enquiry was made had much fallen. Some small objects fell in every instance. (R. Collom.) — The shock was strong, but no lives were lost. The court-house roofs and towers were wrecked, many brick chimneys were down, and communication with other towns was entirely cut off by the breaking of telephone and telegraph wires. Many buildings had their walls shaken down. At the north end of the bridge crossing the San Lorenzo River, at Third Street, there were 4 fissures running practically parallel and almost due east and west. These fissures are about 700 yards in length, and vary in width from 2 to 8 inches. They run thru an apple orchard and are in sandy soil, the softness of the land near the river-bed being apparently responsible for their presence. The river at this place runs about east. In going thru the town of Santa Cruz in the direction of Boulder Creek, a fissure at the intersection of Bulkhead and River Streets was noticed. This fissure was about ― 271 ―
1.5 inches wide and ran east and west. The 90-foot brick smoke-stack of the San Lorenzo tannery, which is about 18 feet in
diameter at the base, was unharmed by the shock. It is said that as far as was observed, there was no change in the appearance
of the sea-level at Santa Cruz; nor was there any damage done by the sea, nor any unusually large waves at the time of the
shock.
At the Southern Pacific bridge, crossing the San Lorenzo River, there is a network of fissures varying from 2 to 15 inches in width, running thru the sandy soil. The direction of the main fissures is east and west, and they are on the south side of the river, which is nearest the bay. The ground has settled about 10 inches from the abutments and piers of the bridge. The depth of the fissures was indeterminable, as they had filled with sand. At Santa Cruz the inhabitants reported that near Olive Springs, 12 miles north of Santa Cruz, a landslide demolished Loma Prieta Mill and killed 9 men. (G. A. Waring.) — The city of Santa Cruz furnishes excellent evidence of the effect of soil formation on the intensity of the earthquake shock. On the high ground in Garfield Park, and also in the northwest part of the city, only about one-fourth of the chimneys fell and a little plastering was cracked; while in the lower ground near the business section several brick and stone buildings were partly shaken down. The San Lorenzo River was churned into foam, the banks cracking and settling several inches; and sand, said to have come from a depth of 100 feet, was forced up in several places. The bed of the river is also said to have sunk several inches, and the current to be slower than before. A 6-inch water-main, running east and west across the river at the covered bridge, was broken at each end of the bridge and moved 5.5 inches eastward. A man out of doors, facing south, was thrown east, then in the opposite direction. A eucalyptus grove south of him swayed violently east and west. Along the beach the shock seems to have been less severe. The running engines of the power-plant at the Casino were unaffected. Things were thrown mostly from the west wall in a curio store on the beach. The wharfinger says he heard a rumble before the shock, coming from the southeastward; and saw the seismic wave traveling shoreward, causing a great rattling and crashing when it struck the town. Two distinct periods of vibration were felt, the latter being the harder. There was very little surf, the water looking like that in a tub when jarred. A safe in the wharf office rolled 3 feet eastward against the counter, then back again hard against the wall. The wharf, extending southeast, seemed to pitch lengthwise. Mr. W. R. Springer, jeweler, reports that out of 25 clocks repaired by him, which had been injured by the shock, 20 had their pendulums thrown off. At the Santa Cruz light-house, a noise as of a wagon crossing a bridge preceded every quake. The motion seemed vertical as well as horizontal, for the glass globe over the lamp was jarred out and broken. In the curio-store at Vue de l'Eau, nothing on the lower floor was disturbed and only a few vases and pieces of bric-à-brac on the second floor were displaced. The shock seemed to come from the south. No effect on the surf was noticed. (R. Collom.) — Going north from Santa Cruz, a small fissure ran northwest and southeast on the Boulder Creek road, about 0.75 mile northwest of the California Powder Works. Along the lower end of this road were several small and unimportant land-slides. In general, the shock in this region does not seem to have been as severe as it was farther north. Road into Scott Valley (B. Bryan). — Following the road from Santa Cruz into Scott Valley, at a summer hotel the chimneys were cracked all the way down, but were still standing; light objects on the first floor were moved, and bureaus on the second floor slid a foot or so. A 1-story frame house (at 53, map No. 22) was moved 4 feet or more, and a piano and other heavy objects were shoved across the room. The damage ― 272 ―
to the house was so serious that it was being torn down at the time of observation. A 4,000-gallon tank (at 54, map No. 22)
was moved and burst open, letting out 2,000 gallons of water. At the house nearest it, the chimneys were cracked, but nothing
inside had been disturbed except some bottles, and no plaster was cracked. Houses in Scott Valley had about this same amount
of damage; chimneys were sometimes cracked but were still standing, and plaster did not fall.
Miss Finette Locke, of Scott Valley, reports that a man was thrown to the ground by the shock, and when he arose could not walk because of the earth's motion. The vibration was northeast-southwest. Everybody was awakened; all clocks were stopt; plastering was extensively cracked; and all chimneys were broken. About a mile north some chimneys fell, and in one house 4 dozen jars of fruit were thrown from shelves. Landslides and cracks are reported between Scott Valley and Felton, and the dam across a small lake was cracked. A statuette and a vase fell to the northeast. The largest chimney moved 2 inches to the northeast. The entire width of the road to the southwest of the small lake was splasht with water thrown out of the lake. Long billows on the lake extended northwest and southeast. In an 8-foot trough orientated east and west water was caused to sway back and forth, but not parallel to the sides of the trough. A neighbor who was awake heard a roaring noise in the northeast. Much milk and cream was thrown out of pans. Going from Scott Valley toward the town of Felton, the shock appeared to grow constantly lighter; some people did not even get out of bed. Felton. — In this village the shock was apparently lighter than at either Boulder Creek or Ben Lomond. At Zayante, some cordwood and some finer split wood, piled 8 feet high, was not shaken down, tho some of it was said to have been disturbed. (R. Collom.) — The shock was only moderately strong. The damage consisted of the destruction of brick chimneys. Earthquake effects at this point are shown only by the damage to artificial structures. Pescadero to Butano Creek (H. W. Bell). — In the town of Pescadero the shock was heavy; all but 3 brick chimneys fell, and but few buildings were otherwise damaged. Plastering was knocked from the walls in most of the houses, and church bells were rung. All the water-tanks observed were still standing, and none of the churches had lost their steeples, tho one church was cracked open. Cracks were visible in the streets. One man walking eastward along the road near Pescadero was thrown flat on his chest by the first shock, but jumped up and braced himself in this direction, and was then thrown southward. Cracks in the road also appeared, and dust spurted up. Several people were nauseated by the motion and some said that a noise as of a wind preceded the shock. Going eastward from Pescadero, a small crack 30 feet long, with an east and west strike, was observed. In an orchard near by there were several cracks, the widest one measuring 8 inches, with a vertical displacement of 1 foot. About 2 miles east of the town, on the north bank of Pescadero Creek, a landslide in the shape of a half-moon, its axis lying N. 23° W., had slipt down toward the bed of the stream. The greatest vertical displacement at the top of the slide was 15 feet; the distance from its apex to the road about 85 feet; and the span from end to end along the road about 220 feet. No solid rock was exposed by the slide. The road had dropt 6 feet at the south end, and 8 feet at the north. Only a few cracks appeared on the surface of the part which had slipt. The creek lying directly below the road had apparently received very little soil from the landslide. Along the stretch of road between this slide and the town of Pescadero, there were few cracks in the road and the houses were in good condition. The only brick chimney seen was down. The intensity was apparently the same as in the village, and continued ― 273 ―
the same along the road leading southeast toward Butano Creek. A 1-inch crack at the first fork of the road a mile from the
town of Pescadero extended north and south for about 50 feet, and a farm house a mile farther down the road was nearly shaken
off its foundations. Dishes fell from the shelves in this house, and water oozed out of level ground near by.
(G.A. Waring.)—On Butano Creek there were slight cracks in the road, and the streams were muddy. People said the shock was felt very distinctly, and dishes generally fell. The houses were all light, low buildings, and were not damaged. At a sawmill a mile east up this creek, there was no damage; and altho the banks beside the road showed traces of caving, there were only slight cracks, the longest one being in the middle of the road above the creek, running N. 67° E. for a distance of about 50 feet. Along the main road from Butano Creek to Little Butano Creek, then across by trail to Pigeon Point, the same effects were noticed. Near a house on the level creek bed of Little Butano Creek, 4 cracks averaging 3 inches in width and about 20 feet in length ran N. 33° E. The only crack noticed along the trail toward the coast was 1 mile northwest of the place where Little Butano Creek turns from southwest to northwest, and was about the same length, but ran N. 3° W. Pomponio Creek road (F. Lane). — On the Pomponio Creek road, chimneys were shaken but not destroyed. A big slide above the last house forced the observer to leave the road and take the trail, which rejoins the road a half mile farther on. Four miles from the town of Pescadero, on the east side of a bridge over Pescadero Creek, the ground had sunk 2 inches and the aperture filled by the land sliding. A mile nearer the town, the road had dropt 5 feet, but had been filled by a big slide. A house at this point was quite intact, but the chicken-house near it was carried down and partly buried by the landslide. On Eues Creek, near its junction with Pescadero Creek, a hillside had started to slide and apparently needed only to become rain-soaked to continue the slipping. Wherever there were buildings in this region, no damage had been done except to chimneys, which had fallen. The Coast from Pigeon Point to Ano Nuevo Bay (H. W. Bell). — At Pigeon Point the brick light-house, 125 feet high, showed a slight crack all the way around inside, about 40 feet from the ground. This crack did not look dangerous. Another crack 20 feet higher up dated from December 17, 1904, the keeper explained. The base of the pedestal holding the lens was slightly cracked, but the lens was intact. In the houses near the light-house the damage was slight; brick chimneys had not fallen, tho slightly cracked, and the same was true of plastering. A mile west of the light-house a few slight cracks, with a direction of N. 28° W., were observed. Leaving the coast road at the fork halfway between Pigeon Point and Franklin Point, and going northeast along Gazos Creek, then southerly to the crossing of Whitehouse Creek, then back again to the ocean road near Franklin Point, few traces of the shock were noticeable. A small landslip, 0.25 mile up the east side of the short creek which flows into Gazos, just west of the fork of the road which continues northwestward to Little Butano Creek, showed a 2-foot vertical displacement at the top, and the land had shoved into the road below. This slide measured 150 feet from its top to the road, and its width at the road was 100 feet. Along this route from Gazos to Whitehouse Creek, 0.125 mile from Whitehouse Creek, at several farm houses brick chimneys were down, houses slightly moved on their foundations, dishes broken, and plastering cracked. A half mile northeast of the mouth of Whitehouse Creek the same kind of disturbance was found. The intensity was apparently uniform with that at Pescadero. At the Cascade ranch, 0.25 mile northwest of Greenoaks Creek, the shock was even stronger than on Whitehouse Creek. Cows were thrown off their feet, chimneys were down, the house cracked, and nearly all plastering fell off. ― 274 ―
(H. W. Bell.) — It was reported here that along the Ocean Shore construction work near Bolsa Point, a concrete pipe 24 inches in diameter and 6 inches thick, embedded in clay, had been cracked by the shock. The keeper of the Ano Nuevo light-house says a distinct rumbling preceded the shock, which came at first rather gently, followed by a hard, confusing shake. A brick chimney in the house near by was cracked and twisted 0.75 inch out of place, but the new tile and concrete building was unhurt. The ocean became no rougher, but had a peculiar greenish hue for several days after the shock. At Pigeon Point the shock was less severe, and little damage was done to the buildings, altho cracks in the light-house, caused by a former quake, were opened somewhat wider. Following the road from the Cascade Ranch across toward Ano Nuevo Bay, the intensity seems to have decreased. At a house 0.75 mile southeast of where the coast road crosses Greenoaks Creek, a few dishes fell; plastering was but slightly cracked, and a water-tank stood. Half a mile north of the mouth of Ano Nuevo Creek, the brick chimney was knocked from a house, plaster was cracked, and cattle were caused to stagger. Half a mile southeast of where the main road crosses Finney Creek, a ledge of shale had been knocked into the gulch. The largest piece which fell had an unbroken surface of about 4 square feet. The almost horizontal edges of shale beds near a house at this point were knocked down. A long, narrow landslide above a house 0.75 mile northeast of the mouth of Waddell Creek had landed against the end of the house, taking out a strip of earth below a spring and causing a good supply of water to issue forth. This slide appeared to be partly due to the large amount of water present. At the house the chimney was cracked, but dishes did not fall from their places. Turning north by a trail opposite Greyhound Rock, evidences of about the same intensity were found. Dead trees had fallen here and there, but in no uniform direction. Los Gatos to San JuanLos Gatos, Santa Clara County (I. H. Snyder). — Los Gatos, population 1,900, is partly on a mountain slope and foot-hills, and partly on river deposit. It is surrounded by hills on three sides. Los Gatos Creek runs thru the center of the town from south to north. The earthquake shock was violent, but apparently not so severe as in the central portion of the valley. Nearly all business houses were damaged, and about one-third of the plate glass fronts were broken. Much plaster fell both in Los Gatos and in the surrounding country. Chimneys fell in many different directions, and nearly half of the damaged chimneys left standing were twisted. About 80 per cent of all the chimneys were destroyed or damaged. Brick fronts were nearly all cracked, and one fell out. There were about a dozen upheavals of sidewalks, mostly on north and south streets. Grocers and druggists lost quite heavily in breakable goods. The direction of the shock seemed to be in general north and south, altho there were certainly severe vibrations from nearly all points of the compass, while some persons are certain that there was a vertical motion, especially near the beginning. After the shock was over, our chandelier was still swinging violently north and south; a near neighbor's lamp swung in the same way; another hanging lamp 0.5 mile west swung northeast and southwest. East and west shelving in stores suffered rather the most, tho a store in East Los Gatos, with shelves north and south, suffered fully as much as any. Of the 3 pianos seen in Los Gatos that were moved, 2 went to the south about 3 feet and one moved east the same distance. A small seismograph made several years ago was in working order, but there was no record, the needle having been thrown off by the extreme movement. Mr. Lund, of Los Gatos, was one of the few people outside when the shock came. He is positive the premonitory roar came from the south and traveled to the north. ― 275 ―
Mr. Dan Pickering, living about a mile south of Santa Clara, on the Santa Clara and Los Gatos road, was standing outside his
barn when he heard the sound, which he compares to a stampede of cattle coming from the southeast. His tank and wind-mill
fell diagonally across the foundation to the northwest, after swaying heavily three times; first to the northwest, then to
the southeast, and finally to the northwest. He states that the ground rose and fell in waves a foot high. Others report that
the orchards seemed to be agitated by a wave-like motion.
On the ranch of Dr. Tevis, about a mile from Alma Station, where the land is rolling and wooded, the ground was fissured and the bottom of an artificial lake was upheaved. (Plate 139C, D.) The cracks and fissures, of which there are many, run mostly north and south, and vary in length up to 100 feet, and in width from 0.5 inch or less to 20 inches. While a good many of the openings were parallel to the slopes and were caused by the ground starting to slide, others crost the roads and could be traced some distance up the banks. A board fence was splintered where it crost a fissure. The upheaval of the lake was caused by a closing together of the sides, shown by the heaving up of parts of the retaining dam at the lower end of the lake. The rise of the bottom is roughly 10 feet. Three of the large cemeteries of the Santa Clara Valley were visited. In the Los Gatos Cemetery, on the New Almaden road, no monuments were thrown. In the Protestant Cemetery, 0.75 mile southwest of Santa Clara, 31 monuments were thrown down and mostly broken. Of these 10 fell to the south. In the Catholic Cemetery, 0.25 mile nearer Santa Clara, 26 monuments fell, of which 10 fell to the south. The direction of the fall of monuments in these two cemeteries is here tabulated:
In the Catholic Cemetery three monuments were turned on their bases, two clockwise and one counter-clockwise. The Santa Clara city water-tower, with large tanks on top, fell to the southwest. (F. H. McCullogh.)—I was in bed in Los Gatos and was awakened by the shock, which seemed to be a violent but irregular shaking back and forth in a northeast-southwest direction, altho objects were overturned in an easterly or southeasterly direction. A double bed on a polished floor rolled 4 feet from its position. One heavy marble clock was thrown off its shelf. Ornaments and bric-à-brac were thrown down. Two tables were turned upside down. Plastering was cracked. Chimneys were cracked above roof, but not thrown. In the town I could hear of only one chimney which was uninjured; 90 per cent of all chimneys were thrown down. Water in a reservoir 30 feet in diameter and 10 feet deep was thrown out so as to lower the level of the water nearly 2 feet. Lexington (H. R. Johnson). — At the Lexington saloon, 3 miles south of Los Gatos, very little damage was done. At the Averill place, 1.5 miles west of Wright's Station, a water-tank was moved a foot toward the south. A piece of board several feet long, which was leaning against the tank-house before the shock, was said to have been found wedged between the bottom of the tank-house and the foundation. This would necessitate a lifting of the tank-house in a vertical direction on that side, which might have been accomplished by the tank-house rocking from side to side. Summit Hotel (H. R. Johnson). — At Summit, a summer resort, the new hotel and several small cottages were all thrown toward the north. The main fault fracture is ― 276 ―
about 500 feet northeast of the hotel, and a secondary crack close to it had a downthrow of from 5 to 7 feet on the north
or downhill side. The crack was about 4 feet wide here, and the line of fracture was parallel with the direction of the ridge.
The Summit school-house was dropt 4 feet downhill from its original position toward the northeast. In the vicinity of Summit
several redwood trees were snapt off.
Just north of Wright's Station, on the west bank of Los Gatos Creek, there was a landslide 0.5 mile wide which had slid into the creek and dammed it. The top of this slide was near the Summit school-house and was close to the main fault-line. The Hotel de Redwood was destroyed by the shock. Wright Station (Miss F. C. Beecher). — Miss Beecher's home is on Loma Prieta Avenue, on the county line, 1.5 miles in an air-line from Wright's Station. The house stands on a ridge at an elevation of 1,700 feet. There were 2 maxima in the shock, of about equal intensity. The movement in the first was from south-southwest to north-northeast. All light objects were thrown down. Furniture against south walls was thrown down or moved out; objects against other walls were not moved as much. A small square piano which stood a few inches from a northeast wall ran back against the wall to the north with sufficient violence to break a knob off one leg. It then moved back to its original position, then 5 inches west. Then the two legs to the north jumped 6 inches south. These movements were determined by the marks upon the floor. A wash-basin, and a pitcher full of water, in an upstairs room, were thrown south, and the basin was found with the pitcher standing in it, uninjured but empty. A table in the middle of the same room fell to the north. A piano in a neighboring house, a heavy upright, was moved across the room to the northeast. All brick chimneys on the ridge fell, mostly to the north. Trees at the foot of the ridge were bent over to the north-northeast. Half a mile to the northwest of the house, a fissure 2 feet wide appeared, from which bad-smelling gas emanated. The fissure runs from north to south, and the earth was piled up on the west side from 2 to 4 feet high across the road. On Highland, a mile to the west, a fissure 5 feet wide was opened at an altitude of 2,500 feet. A building standing close to a fissure was entirely uninjured, while others a little farther off were wrecked and one collapsed. Most good buildings in a belt 0.5 mile west of the house were wrecked, while barns and shaky buildings stood. About 1.5 miles west, a house split open. Gulches appear to have been contracted, as the bridges crossing them show that they were squeezed. The banks of Burrell Creek appear to have approached each other, so that the creek has become very much narrowed. Water-pipes were broken and twisted, and filled with dirt. Water was thrown out of tanks, but the tanks were not overthrown. During the shock the waves appeared to oscillate in a north and south direction at first. There were at least 26 shocks during the first 26 hours after the main shock. Burrell School (H. R. Johnson). — Near the Burrell school-house, 1.5 miles southeast of Wright Station, a crack extends across the road by a blacksmith shop and shows a downthrow of 4 feet on the northeast. The blacksmith said there was a strong odor of sulfur for 5 or 10 minutes after the shock. A well near by has had sulfur in the water for a number of years. Morrell Ranch (H. R. Johnson).—The Morrell ranch is located 1 mile south of Wright's Station and is on the line of the fault. The house itself was built exactly upon a fissure, which opened up under the house at the time of the earthquake. The house was completely wrecked, being torn in two pieces and thrown from its foundation. (Plate 107B.) There was an apparent downthrow upon the northeast side of the fault, as seen in the orchard; but under the house the vertical movement was not so apparent. An especially strongly constructed wine cellar built into the side hill had the upper portion thrown 3 feet northeast, directly away from the fault-line. After the shock this upper portion ― 277 ―
of the house was left resting upon the wine tuns, and not upon its original upright supports (fig. 56). The fence and road
near the house were crost by the fault and showed an offset which indicated a relative movement of the southwest side toward
the southeast (plate 64B). One fence was broken apart, but the other was merely bowed, due probably to the resistance and
drag of soil occasioned by a well-packed roadbed. The fruit-tree rows which crost the fault-line at approximate right angles
were put out of alinement.
A feature associated with the movement of soil along the fault-line is shown in the accompanying sketch, fig. 57. The "splintering" of the main fracture raised a long, low ridge across which a creek had been forced to cut its way thru a vertical distance of 1.5 feet to get down to its original level. Between Wright's and Alma the railway track was buckled. (See plate 107A). (D. S. Jordan.) — At Morrell's ranch, about 4 miles above Wright's, a large 2-story house with a wing stood on the slope of a hill. The east side of the house was much higher above the ground than the west, and stood on wooden piers about 7 feet high. The earthquake crack past thru this ranch, a branch of it going under the house. The main body of the house was thrown to the east, away from the crack, the ground there slumping several feet and the house being almost totally wrecked. All thru the orchard the rows of trees are shifted about 6 feet, those on the east side being farther north, and the east side, which is downhill, seems to have fallen. The crack is largely open and in one place is filled with water. This should be attributed to slumping. A little farther on, the crack passes thru a grassy hill on which there is no slumping. The Morrells say that this hill has been raised. What appears to be the fact is that the east side of the hill overrides the other. The whole top of the hill is more or less cracked for a width of about 10 feet. The east side is a little higher than the west side, and it looks as tho the hill had been shoved together and raised, the east side overriding. About 1 mile beyond Morrell's house, at the end of the ranch, there is a blacksmith shop, and the road is crost by the crack. Here there is a break of 3 or 4 feet like a waterfall, the east side being the lower; but this is part, I take it, of the general slumping of the east side of the crack ― 278 ―
where it stands near the ravine above Wright. Morrell's place is right over the Wright tunnel, the tunnel and the rocks near
by being of finely broken rock and very much subject to slides and other breaks. At Freely's place, 4 or 5 miles north of
Morrell's, some 15 acres of woodland have slid into Los Gatos Creek, making a large pond. There are many other slides in the
neighborhood and many broken trees. Farther on, the crack goes into Hinkley's Gulch, in which the Loma Pricta Mills are situated,
and which are buried under the slides. The slides which obliterated Fern Gulch at Skyland do not seem to have come from the
crack, but seem to lie to the west of the crack.
About four miles south of Wright Station (Mr. L. E. Davidson). — I was camping in the Santa Cruz Mountains. My attention was first arrested by a slight rumbling noise; then the house trembled for 4 or 5 seconds, and this was followed by a heavy rolling motion almost east and west. A heavy trembling came again for several seconds, then the heavy shock that threw down the chimneys. Tables and even chairs were upset. This must have lasted about 4 seconds; it then gradually died away. The whole time must have been all of half a minute. During the day several slight shocks were felt; about 2h and 2h 30m P. M., two rather heavy shocks came. The ridge on which we camped was full of cracks, ranging up to 2 and 3 feet in width, and in length from a few rods to 0.25 mile, all trending west of north to northwest. All chimneys on this ridge were thrown down; several houses were completely wrecked; branches were broken from the trees, while many of the trees broke in two and others were uprooted. The canyon south of us was filled with landslides. In this canyon the stratification of the rocks is plainly shown. The strike is northwest-southeast and the dip is almost vertical. The cracks coincide in direction with the strike of the strata. Cold water was flowing from some of the cracks. I obtained a small bottle of crude oil from Mr. Sutton, which he said was dipt up from the ground on his neighbor's ranch, several hundred gallons of oil having run out of the ground since the earthquake, where there had been no sign of oil before. Skyland, Santa Cruz County (T. Wightman). — Mr. Wightman's bed traveled across the room to the south, and he was under the impression that the house was falling to the south. Some houses in the neighborhood fell completely, and some collapsed on their foundations. The two chimneys of his house were thrown, one coming through the roof. Some pictures hanging on east walls were turned with their faces to the wall. Large landslides occurred in the neighborhood. Soquel, Santa Cruz County (Miss M. E. Baker). — The house is on the first high bench above the stream in Soquel Valley, with high hills to the north and the east. At the first movement of the earthquake, chimneys were thrown to the south; at the second, mantel ornaments, books in the library, fruit jars in the pantry, etc., were thrown toward the north. Some houses in the vicinity had chimneys and objects partly turned around. There were two maxima in the shock, the first being the stronger, and the direction of movement was from north to south. In the second part of the shock the movement seemed to be a twisting one. Chittenden (G. A. Waring). — At Chittenden Station evidence of a most violent disturbance was found. The cottage of the foreman was moved 5 inches westward; an upright piano was thrown northwestward upon its back, and electric drop-lights swung so as to break against the ceiling. A large frame dairy building on underpinning was moved 3 feet northward, as was a smaller building. The oil in a large tank was thrown southeastward, badly bending the tank and smashing the protecting shed. (See fig. 58.) The railroad office was not moved from its foundations, but the porch roof was jerked nearly off and a 1,000-pound safe was thrown southeastward upon its back. Three freight cars on the side-track, loaded with beans, were tipt over to the northeastward. At the time of the shock a north-bound freight train was running at ― 279 ―
about 30 miles an hour, a short distance south of the bridge over the Pajaro. About 10 cars in the middle of the train were
thrown off on both sides of the track. The track at the southern end of the Pajaro bridge sank from 2 to 4 feet for a distance
of 150 yards, and between Chittenden and the bridge the track was bent in an S-shaped curve in several places. The concrete
piers of the bridge were cracked, and the granite cappings shifted as before noticed. (See plate 65B and fig. 43.) There is
much sulfur, oil, gas, and water in the hills here. A marked increase was noted in the flow of oil and water, and more gas
and sulfur became associated with them. It is said that since the earthquake 16 years ago small shocks have been felt each
spring, often severe enough to crack chimneys, and a deep well becomes muddy 2 or 3 days before these occur.
Fifty-two distinct shocks were felt during the day of April 18, and 32 that night. From 1 to 4 shocks were felt every day thereafter up to May 16, and from 2 to 5 occurred every night. Two miles north of San Juan, Mr. Canfield's house, at the foot of the hills 0.5 mile east of the fault, was moved bodily 2 inches westward, and the chimneys were completely thrown down; but a house 150 yards west of the fault, altho considerably shaken, appears to show the shock to have been less severe on that side. San Juan (G. A. Waring). — The town largely escaped by virtue of being on solid ground. A large inner wall at the San Juan Mission fell, but it was no doubt weak, as other parts of the building appear unhurt. Only one or two chimneys in this village fell, but in the bottom-land between San Juan and Hollister the condition of the houses indicates a heavier shock on the low ground. Santa Clara ValleyInformation regarding the distribution of intensity in Santa Clara Valley has been contributed by a number of observers whose names are given with the paragraphs dealing with the respective localities reported upon by them. Newark (F. E. Matthes). — Nearly all brick and tile chimneys in the village were broken off; the direction of throw varied. Plaster cracked and fell in quantities on the lower floors of hotels and several other buildings. There are no brick houses in the town; and most of the frame dwellings showed no effects of the shock. At the depot the ― 280 ―
water-tank fell, the supporting trestle being practically demolished. The track suffered a slight shifting in several places
north of the village. Cracks opened in the ground in the vicinity of 2 small watercourses, but on a less extensive scale than
that noted at Alvarado. Some of them crost the railroad track. In every case they emitted the same bluish sand (with the water)
that had been found near the Alameda Sugar Mill. In one place, 1.5 miles northeast of the village, considerable water was
still left standing in shallow ponds. According to neighboring ranchmen, these ponds had not existed prior to the earthquake.
Centerville (F. E. Matthes). — The amount of destruction here seems greater than in the neighboring towns, but this is in large measure due to the presence of a number of poorly constructed brick houses. All of these had suffered severely, the walls being in part thrown down. The bank building was more seriously damaged than most buildings, the walls being partly demolished and the roof having caved in. With very few exceptions all the brick and tile chimneys were broken off. Window panes broke in several stores. No cracks in the ground were found or reported. The direction of the shock was not agreed upon by the residents; according to some it was north-south, according to others east-west. Mission San Jose (S. Ehrman). — Nearly all chimneys were thrown down, and plaster in houses cracked; the direction of the throw of chimneys and objects being chiefly from north to south. Some objects were rotated clockwise, and hanging objects were caused to swing. Irvington (F. E. Matthes). — Destruction similar in degree to that at Centerville. Every brick house was more or less extensively damaged; portions of walls fell in some instances, and cracks in brickwork were common to all. The large brick and stone buildings of the Palmdale Winery suffered more severely than any, and large portions of them will have to be rebuilt entirely. Only a few chimneys were left standing in the village. Plaster cracked and fell in large flakes in several houses. The upper stories apparently suffered less than the lower floors. Milpitas (F. E. Matthes). — Nearly all chimneys were here thrown down, a few, including a very short one on the depot, being left intact. There are no brick buildings in the village and the destruction seems insignificant. The hotel slipt on its foundations, but was almost repaired at the time of the visit. A small adobe house in the southern part of the village was fairly demolished; it was known to be an old and weak structure. A water-tank and wind-mill were thrown down, support and all, about a mile south of town. They fell to the south. Another tank, north of town, appears to have fallen to the west. Several other tanks in this neighborhood were found intact. Of the two bridges over Coyote Creek, the northern one suffered some damage by displacement of end supports. It was unsafe to travel over at the time of the visit. The southern bridge was found intact, the end supports showing signs of but small movement. Agnews (F. E. Matthes). — The insane asylum, consisting of three tall and three minor brick buildings and some small frame structures, suffered very severely. Every one of the brick structures was damaged beyond repair and will have to be entirely rebuilt. The main buildings were long, 3-story brick structures oriented north and south, with large projecting bay windows at their north and south ends. These were destroyed, so that both buildings are open at their ends. The fall of these walls caused the caving in of the roof, and the sagging down in some places of the floors. Numerous lives were lost; in all 112 dead being found in the ruins. The administration building was partly wrecked by the fall of its tower, which crashed thru the roof and all the floors, carrying with it a number of people. In nearly all cases the north and south facing walls were thrown out, while the east and west facing walls were, as a rule, better preserved. The shock seems to have been north-south principally, judging from these data. ― 281 ―
The tall brick chimney of the engine house (100 feet high) broke off 20 feet above the ground and fell in a northeasterly direction, without touching any other structure. Frequently window-panes remained unbroken in the lower parts of walls whose upper parts had been completely demolished. (See plate 108A, B.) The extent of the destruction is in some measure due to the use of weak mortar, the bricks having, as a rule, fallen separately rather than in aggregates. It is believed that well-built buildings would not have suffered such wholesale destruction as was witnessed here. Alviso to Milpitas (G. F. Zoffman). — Evidences of the earthquake at Alviso are shown only by fallen chimneys and cornices and by cracked walls of the brick warehouses. No buildings were demolished and little serious damage of any kind was to be noted. From 1,500 to 2,000 feet west of the bridge over Coyote Creek, cracks cross the road in front of the Boot ranch-house, and several of them occur in the road leading to that house. (Plate 140B.) Some of these cracks are about 6 inches wide and have a general bearing of N. 43° W. Immediately after the earthquake, water flowed from some of them and brought up sand, which was heapt up about 6 inches high. The water ceased to flow after the second day. Near the dwelling house on the Boot place, the ground settled 11 inches on the east side of the crack. The fissures past under the corner of the dwelling house and the building was partly thrown from its foundation. The cellar beneath it was filled with water to a depth of from 2 to 3 feet. There is a capped artesian well in the yard of this house, and about this well is a pool of water 12 feet across. The west side of the pool was lifted 1 foot higher than the east side, and fish were thrown out of the pool. A hundred feet east the fissures past under the barn, and the ground settled on the west side. Water flowed from cracks in the yard and piled up sand 6 inches high on both sides. People living near Coyote Creek state that the water rose between 2 and 3 feet immediately after the earthquake; and up to April 26 the water in this stream had not returned to its normal level. At the bridge over Coyote Creek, on the Alviso-Milpitas road, the concrete abutments were thrust inward toward each other about 3 feet. A pile driven in the middle of the stream, which had been cut off below the water-level, was lifted about 2 feet and now rises above the water. About 150 feet north of this bridge the banks of the stream cracked, the fissures running parallel with the channel and the land on the creek side sliding toward the stream. (Plate 140A.) West of the stream, in an adjoining field, water rising thru cracks built up many craterlets of sand. (Plate 143A.) Residents of the vicinity state that the water rose 3 or 4 inches above the tops of these craterlets while they were being formed, and that it ceased to flow toward the end of the second day after the earthquake. In the road running northward along the west side of Coyote Creek from the bridge, many large cracks opened. Five hundred feet north of the bridge the cracks were 2.5 feet wide and 3 feet deep when the place was visited April 26. Farther north the cracks were very abundant, mostly parallel with the road, and some were 4 feet deep and 3 feet wide. A quarter of a mile north of the bridge, the whole road was shoved eastward into the channel of the creek, and with it a large number of willows and cottonwood trees that grew along the banks. Just south of this place the road was broken up badly for a distance of 300 feet. One of the largest cracks in the road was 5 feet wide, 6 feet deep, and more than 100 feet in length. The bearing of the fissures at this place was N. 23° W. For the most part the principal features were approximately parallel with Coyote Creek. At Mrs. North Whitcomb's ranch, on the south side of the Alviso-Milpitas road, between Coyote Creek and Milpitas, the prune orchard was cracked and the ground shifted ― 282 ―
at several places. The ranch-house, of concrete with a wooden upper story, was cracked across the northwest corner and settled
slightly on the northwest side. In the back yard were fissures 1 foot wide, running about N. 13° W., with a downthrow of 1
foot on the east side. Some of the prune trees in the orchard are 2 feet out of alinement, and some as much as 6 feet. The
lateral displacement here shows a relative movement of the south side toward the east. Considerable sand was brought up by
water flowing from the cracks in this orchard.
In the town of Milpitas all the chimneys were thrown down, as well as 3 frame buildings. The hotel fell from its underpinning and sank bodily about 3 feet. The streets near it were not disturbed. Warm Springs (G. F. Zoffman). — The Warm Springs Hotel, a large 2-story building, was but slightly damaged, only a little plaster falling. No buildings were damaged, beyond the falling of two chimneys. Milpitas-San Jose Road (G. F. Zoffman). — About 0.5 mile south of Milpitas, on the Milpitas-San Jose road, cracks were formed across the road. They did not, however, appear to have any definite direction, and were so small that no lateral movement was discernible. At the County Alms House, about 1 mile south of Milpitas, two chimneys were thrown down and considerable plaster fell. On the north side of the bridge which crosses Coyote River, on the San Jose-Milpitas road, some cracks were found but they were evidently caused by the sliding of the banks. The bridge was not damaged. The damage in the section of country lying between Milpitas and San Jose was nearly uniform. About 90 per cent of the chimneys were thrown down and in all houses that were plastered considerable plaster fell. Articles in the houses were thrown over, and much water and milk was spilt, altho it does not appear to have been in any particular direction. Cracks like those which were observed in the ground on the Milpitas-Alviso road reappeared on both sides of the Coyote River at intervals all the way to San Jose. Altho they occur in a general north-south direction, it seems probable that their origin was due to the unstable condition of the alluvial deposits which underlie the valley. Alum Rock Road (G. F. Zoffman). — Starting from San Jose and going toward Alum Rock, it was observed that the shock had decreased from an intensity of IX at San Jose to an intensity of VI at Alum Rock. No cracks were found between Coyote Creek and the mountains, but in the valley at least 90 per cent of the chimneys were thrown. At the mouth of the Alum Rock canyon, a count of the fallen chimneys revealed the fact that the percentage had dropt to 50. At Alum Rock no chimneys were damaged nor had any movable objects been overturned, altho the water in sulfur baths had splasht up about a foot on both sides. Calaveras Valley to Evergreen and vicinity (G. F. Zoffman). — Going from Milpitas toward the Calaveras Valley, chimneys were all thrown down on the flat lands between the village and the foot of the grade leading over the ridge to Calaveras Valley. In Calaveras Valley all the brick chimneys were thrown down, tho there were only a few in this valley. No damage to houses is reported. Mr. Hadsell, in charge of the property of the Spring Valley Water Company, which has begun to construct a dam at the north end of the valley, states that there was no shifting of the strata in the tunnels, and that no damage had been done the property. Between this place and the head of Alum Rock Canyon, the residents stated that cracks appeared across the road in several places; but altho this was in the proximity of the Calaveras Valley fault-line, which passes thru this region, it was not possible to verify their statements. Mr. Robert Ingleson, who lives in section 22, on the ridge east of Calaveras Valley, reports that the shock was not severe there. A long slender bottle standing on a table in his house fell over, but a lamp on the table was not upset. ― 283 ―
Water in a horse-trough spilt out, and the trees waved as if there had been a wind. The earthquake consisted of two separate
shocks, accompanied by a roaring sound that seemed to come from the north. Springs near his house became muddy after the shock
and remained so for 2 or 3 days. The flow of the springs increased to about four times the usual amount.
Along the road down Penetencia Creek, a considerable amount of débris had slid into the road, in many places obstructing all travel except for pedestrians; but no evidence of cracks could be found. In the region between Alum Rock and Evergreen, about 50 per cent of the chimneys were thrown down, but none of the buildings were materially damaged. As the Santa Clara Valley was once more approached, the intensity of the shock perceptibly increased. At Evergreen, about 1.5 miles from the foot-hills, considerable damage was done; all the chimneys, all the road tanks, and nearly all of the wind-mills in the neighborhood fell. None of the houses were demolished, but some were shifted on their foundations. (H. R. Johnson.) — The Pierce ranch-house, 3 miles southeast of Evergreen, was badly shaken; plaster and chimneys were down and much chinaware was broken. This house is on the gravel of the large alluvial cones which have been built out along the southwest face of the Monument Peak Range, where the stream debouches upon the plain. A water-tank fell northeast and southwest where the Tully road crosses the Coyote River 1.5 miles northeast of Oak Hill Cemetery. At the Mayne ranch, 3 miles south of Oak Hill Cemetery, where the New Almaden Railroad crosses the Downer road, water from tanks and troughs was split in a northwest and southeast direction. To the west of the Mayne ranch, at the Downer ranch, a water-tank fell to the west. Mr. Downer said that milk in pans was spilt in the same direction. At the Poncelet ranch-house, on Llagas Creek, 7 miles southwest of Madrone Station, only one chimney fell and no dishes were broken and no clocks stopt. This place is only 3.5 miles northeast of the fault-line and is situated directly upon rocks of the Franciscan series. The Saunders ranch is 3.5 miles southwest of Madrone, on the Madrone road. The shock was quite heavy at this place; the chimneys were thrown down, dishes broken, and portions of what appeared to be quite solid and massive rock outcrops were thrown from the steep hills near the house. South of the Saunders place, 1.5 miles, a water-tank was thrown down. Santa Clara (G. F. Zoffman). — Nearly all the brick chimneys were thrown down and most of the brick buildings were damaged. At Santa Clara College the rotary motion of objects was shown by the turning of statues in the chapel thru an angle of 130°. In the library of the same institution four marble statues, with square bases, fell in three different directions; one facing S. 87° W., another facing N. 87° E., fell toward each other, while the others, facing, respectively, N. 3° W., S. 3° E., fell N. 3° W. Professor Ricard, of the Science Department of the College, states that the vertical movement threw a wind-gage out of a socket a foot deep. This was the only evidence at the College of vertical motion. Cemeteries (G. F. Zoffman). — A count was made of the number of tombstones thrown down in the Santa Clara Cemetery and the various directions in which they fell were noted. From these observations it seems that the shock was slightly more intense toward the easterly direction than toward the westerly. Twenty-five headstones were down and their respective directions of falling were, 3 N. 17° E.; 1 N. 32° E.; 1 N. 37° E.; 2 N. 62° E.; 1 N. 77° E.; 1 E. 17° S.; 1 S. 58° E.; 6 S. 28° E.; 3 S. 23° E.; 1 S. 3° E.; 1 S. 37° W.; 1 S. 42° W.; 1 N. 88° W.; 1 N. 73° W.; and 1 N. 13° W. ― 284 ―
At Oak Hill Cemetery the larger percentage of tombstones fell in an easterly direction. Out of 34 monuments overthrown, 21 fell toward the east or nearly so; 6 toward the west or nearly so; and 1 toward the north or nearly so; 3 fell northeast, one fell northwest, 1 fell southeast, and 1 fell southwest. Out of 6 round monuments that were noted, 4 fell toward the east, 1 northwest, and 1 north. Since these could fall in one direction as quickly as another, it is evident that the greatest movement of the quake must have been toward the east at this particular place. At the Catholic Cemetery, about halfway between San Jose and Alum Rock, only a few monuments were overturned; they fell as follows: 2 north, 3 south, 1 northwest, 2 east, 1 west, 1 southeast. San Jose (G. F. Zoffman). — The earthquake threw down many brick and stone buildings (plates 108C, D, 109A, 110B, 111, 112, 113), and with the exception of 4 or 5, damaged all the rest of the brick buildings, more or less. (Plate 110A.) The damage done to frame houses was proportionately far less. Forty buildings were counted, however, that were thrown off their foundations and damaged to a greater or less extent. In many instances these buildings were completely demolished. (Plate 109B.) Numerous wind-mills and tanks capsized, while at least 95 per cent of the brick chimneys thruout the town fell. Movable objects, such as pianos, were in most cases wheeled out into the room, but there did not appear to be any general direction in their displacement. Water and mud in many instances are reported as having spurted from the artesian wells, but in a few days they resumed their normal condition. The plate-glass windows on the south side of First Street were cracked much more than those on the north side. This phenomenon was not noticeable on the other streets. Data were obtained of the directions in which the chimneys fell thruout the town. After the data were collected and tabulated as shown below, it became evident that chimneys usually fell with the slant of the roofs. In order to group the directions in which chimneys fell, the circle was divided into 8 sectors, of 45 degrees each, starting from the bearing of First Street, namely N. 30° W. The general directions of these sectors are: N. 15° E.; S. 15° W.; S. 75° E.; N. 75° W.; N. 60° E.; N. 30° W.; S. 30° E.; and S. 60° W. Then the direction of the falling of a chimney was taken according to the sector toward which it fell. The streets in the main part of town run either parallel or at right angles to First Street. Since the bearing to First Street is N. 30° W., that of Santa Clara Street (at right angles to First) is N. 60° E. Generally the slant of the roofs of the houses that face these two streets will be N. 30° W., S. 30° E., N. 60° E., and S. 60° W., respectively. It was in these four general directions that the greatest number of chimneys were thrown over. The eight general directions are as shown on the following table:
― 285 ―
(E. C. Jones.) — There was only one broken gas main in San Jose, caused by the high wall of the building falling over; the bricks penetrated thru the soft earth to the main and broke it. At the gas station, the brick retort house was very badly damaged. The north and south gable ends fell out. The brick work at all 4 corners loosened for about 10 feet down to where the roof trusses are anchored in the walls. The superheater of one of the gas-making machines settled on the south side so that it was 2 inches out of plumb. The weight of this machine is about 78 tons. Some of the cast-iron connections in the building were broken. The purifying house, also of brick, was totally destroyed; all the walls and the roof collapsed, carrying the machinery to the ground and destroying it. The relief gas-holder was full of gas at the time of the earthquake and was badly damaged. Two of the cast-iron columns were broken off in several places; portions of the railing fell thru the crown of the gas-holder, permitting the gas to escape. The distributing holder was three-fourths full of gas at the time of the earthquake. The movement threw about 12 inches of the water out of the holder tank. The carriages on the lower section were all broken, these being of cast-iron. The upper carriages, made of wrought iron, were strained but not broken. Considering the violence of the disturbance at this point, it is surprising that the mains did not suffer more than they did; but the breaking off of pipes in the buildings and the crushing of meters under falling houses necessitated shutting off the gas thruout the city for 24 hours. (W. S. Prosser, C. E.) — Over the San Jose area, as a whole, the wreckage seems to have been thrown in all directions; but in certain places some slight system appears. It seems clear that no statement as to direction, amount, or even duration of motion applies to more than a limited area. The only clear cases of rotary motion seen by me were two cases near my home, 2 miles northwest of the center of town. One tank-house turned exactly halfway round, as well as upside down, and one chimney turned about 4 inches, both in the direction of the hands of a clock. Both rotary and vertical motions were felt by many, however. About 500 yards from me is a square brick fence-post 7 feet high, of which 2 feet moved about 3 inches to the southeast (S. 44° E.); or rather, the bottom moved the reverse way. On Stevens Creek road, leading southwest from San Jose, 5 or 6 water-tanks on the roadside fell. One of these seemed thrown to the northeast, but others were twisted and scattered as tho by a mixture of all motions. In some places most of the buildings, perhaps, fell to the north or northwest. In Chinatown (north of San Jose) it was the north and south brick walls that fell. In San Jose most of the clocks on east and west walls did not stop, but many of those on north and south walls did; showing an east and west motion. The brick 7-foot wall around the yard of Nôtre Dame School in San Jose, on the northwest side, fell; but that on the south did not, altho it was cracked. The streets in the central part of San Jose run N. 60° E. The amount of motion differs greatly. In many cases brick work seems to show a sharp blow of 2 inches; sometimes more. The inside east and west wall of the City Hall has a crack of 4 inches. The front of La Mott House (east and west) moved in some places 2 inches, in others 4 inches. The master clock in the Western Union Office (on the ground floor of a large brick building, and on the east and west wall) did not stop, but the pendulum struck both sides of its case many times and with great violence, battering off the varnish. It is long (probably beats seconds) and had to move about 4 inches more than usual in order to strike the case. About 5 miles south of San Jose there were said to be two tubs of water on the ground a few hundred yards apart. No. 1 had most of the water splasht out, but No. 2 apparently had lost none. No. 2 is nearer the hills, and bedrock is nearer the surface. The oil tank at the corner of Stockton and Polhemus Streets, 1 mile northwest of San Jose, splasht over. Many water-tanks did the same. ― 286 ―
Several good observers out of doors are positive that the noise of the quake came from the southeast and died away toward San Francisco. In the afternoon of the 18th, my wife heard the noise of a shock and called out before we felt the shock itself. The noise seemed to come from the south or southeast. Many persons saw waves in the ground. Sifting out exaggerations, these appeared to be rather more than a foot in height. The best observer estimated the distance from crest to crest at 60 feet, others at much less; but I think the waves must have been greater, for there is no evidence in long brick walls showing any such vertical cracks as would have been produced by short waves. Six miles southwest from San Jose, a good observer described the waves as parallel with certain tree-rows which are northeast and southwest, and stated that the waves moved from him at right angles to the line and toward San Francisco. Six miles northwest from San Jose, a man looking south saw the waves (which he thinks were east and west) coming toward him, and hence toward San Francisco. About the middle of the quake these were met by other waves, and the whole surface resembled hillocks, or cross-seas, while the tree-tops waved wildly. To the man southwest of San Jose, however, the tops of the trees were almost still, while the trunks waved sinuously. Near me is a piece of ground 10 by 30 feet, raised about 7 inches; while about 150 feet southeast of this is an area about a yard square which dropt 6 inches. Possibly these represent the crest and trough of an earth-wave. I estimate the duration, I think closely, at between 50 and 60 seconds. The wells of the vicinity seem to show slightly increased flow. One 80 to 100 feet deep has been a little roily since the quake, and one near San Jose was reported as having increased the day before the quake. (M. Connell.) — On the farm of Mr. Fox, 3 miles north of San Jose, the water pipe of an artesian well was broken off 60 feet below the surface and carried by the heave of the land in a northwesterly direction 4 feet from its original position. County road south of San Jose (H. R. Johnson). — At Schutzen Park, 2 miles southeast of San Jose, the shock was felt quite severely. The road house was badly shaken, but very little glassware was broken in the bar-room. A 12,000-gallon water-tank was shifted slightly on its foundations. At this place the first part of the shock was thought to be quite light and the second part heavy; the general motion was said to be from east to west. At the 5-mile house, farther southeast on this same road, there was hardly any damage reported. Even plaster in houses did not fall. There was also little damage at the house 0.5 mile southeast of the 5-mile house. The chimney did not fall, but dishes and lamp-shades were broken. The movement was thought to be northwest-southeast in direction. It was stated by Mr. Russel, of Edenvale, that the shock was lighter there than at San Jose. A well-constructed brick building, which was built 3 years ago, had the roof loosened and the end walls were cracked. About 3.5 miles southeast of the 5-mile house at the Van Every ranch, a chimney fell, plaster on the first floor was badly cracked, and furniture slid around upon the floor. Water was spilt from a tank and a water-trough. Just northwest of the 12-mile house, where the county road crosses to the Fisher ranch, there were cracks from 2 to 6 inches wide in the coarse gravelly bottom of the Coyote River. There was evidence of water having been ejected from these cracks, as there were heaps of clean, fine material surrounding small orifices. It was said at the ranch-house that muddy water came out of these openings following the shock. Half a mile southeast of Fisher's, a water-tank was down. Half a mile south of the 15-mile house, the Barnhart ranch-house, which was set upon wooden underpinning, was thrown from its foundation, so that it rested directly upon the ― 287 ―
ground, 4 feet farther north than its proper place. An old barn and water-tank were uninjured at this same place.
A quarter of a mile south of the 15-mile house, on the county road, a water-tank was thrown down. Going 3 miles northeast from the 15-mile house, Webber's old ranch-house was visited. Here baled hay piled in a barn was shaken down and doors leaning against the house were thrown from their position. Water in both the creek (Coyote River) and a well was muddy after the shock. (H. R. Johnson). — Going northeast thru San Felipe Valley to Smith Creek Hotel, hardly any evidence was seen of damage from the shock. At Smith Creek Hotel no china nor plaster was broken, but two chimneys were thrown down. Los Gatos to Gilroy (G. A. Waring). — Near Meridian, 3 miles west of San Jose, several cottages were shifted from their foundations. All water-tanks on open frames fell, but those that were boarded in stood. The water became muddy in several wells. One lady reports seeing waves traveling southward along the driveway, and a man reports seeing a heavy wagon move 4 or 5 feet back and forth several times, along the driveway. The shock began violently and ended suddenly. The intensity diminished uniformly from Meridian toward Campbell. At Campbell, 68 per cent (51 out of 89) of the chimneys fell, but the plastering in the houses was not badly injured. From Campbell toward Los Gatos the intensity slightly increased. At Los Gatos 78 per cent (67 out of 86) of the chimneys fell. At the distillery 4 miles west of Los Gatos considerable damage was done. The second floor was moved about 18 inches toward the northeast, causing the wall to bow out on the northeast side. Many of the large vats holding 2,000 gallons were shaken off their supports and several were broken by the fall. The shock in Los Gatos, however, was not so sudden as to cause serious injury to brickwork or plastering. The business part of the town is built on 40 feet of gravel overlying shale. Only two stones in the Los Gatos Cemetery were shifted. At Alma the shock was of about the same intensity as at Los Gatos. Milk in pans was nearly all thrown to the north and south. The Morrell house (see plate 107B), near Wright Station, is directly over the fault and suffered more than any other place in the vicinity of Wright Station, tho at least 5 other buildings between Patchin and Skyland were badly wrecked. Going from Los Gatos toward Edenvale, the shock was somewhat lighter than at Los Gatos, judging by the effect on chimneys, plastering, and movable objects; but at Edenvale it was a little stronger than at Los Gatos, as shown by the damage done to the large brick canning factory. All the walls were badly cracked and the tops of the walls fell. The top of the fire-wall above the roof was shaken down. Continuing to the southwest thru Coyote, it was about the same as at Los Gatos, diminishing a little thru Madrone, Morgan Hill, and San Martin, where it had about the same intensity as at Los Gatos. Near Coyote a man reports having seen a northwest-southeast fence move in wave-like fashion, beginning at the southern end; and he heard a noise coming from the southeast and seeming to pass over him. Another man driving along the road near San Martin, heard a roar and his horse became frightened, before the shock came. Clouds of dust arose in the road and the creek near by was rendered muddy by the shock. At Morgan Hill about 64 per cent (18 out of 28) of the chimneys fell, and a 1-story concrete-block building was badly damaged, the whole front having fallen out. A 2-story reënforced concrete-block building was not damaged. At Bucker, 3 miles north of Gilroy, the shock seems to have been about the same. The school building was badly damaged, and several windows were broken by the twisting of the frames. At Gilroy nearly every chimney fell, fire-walls of brick buildings were thrown down (plate 114A, B), and shelf goods were largely shaken down. In the Masons and Odd Fellows Cemetery, out of 120 stones over 3 feet tall, 31 fell. A cylindrical shaft fell north, and a square one fell south, but all the rest fell east or west, tho the tall slabs ― 288 ―
necessarily fell east or west because they faced east. Two marble shafts about 8 feet high were broken off halfway up, the
lower part and base being unshifted. In the Catholic Cemetery 10 stones out of 67 fell.
In the hills between Los Gatos and Gilroy the shock seems to have been somewhat less severe. At the New Almaden mines, the tops of 2 brick furnace chimneys, about 50 feet tall, were broken off; but the furnaces were unharmed and the underground workings unaffected. About 70 per cent (16 out of 23) of the chimneys in the settlement here (Hacienda) were broken off. A loud noise like thunder is reported to have traveled northward down the canyon, distinctly preceding the shock. This has often been heard since, seemingly underfoot, even when no shock has been felt. Southward from New Almaden thru the hills the houses on alluvial land suffered noticeably more than those on more solid ground. From Uvas westward to the summit, the intensity rapidly rose as the fault was approached. Two miles west of Uvas P.O., and half a mile east of the summit, an east-and-west stone wall, built of loose boulders, was thrown mostly northward; water was thrown from troughs toward the north; and all streams were muddy for 2 days after the shock, while in wet places there was a noticeable settling of the ground. Southward from New Almaden along the eastern side of the valley, the shock uniformly lessened in its intensity thru Old Gilroy and San Felipe to Hollister. At San Felipe a large stone cheese factory was not damaged, except for a few cracks. The lake 0.5 mile west of the village was considerably stirred up, and water from a full road tank was thrown 60 feet across the road. A considerable rumble was heard all thru this region; one person says it came from the southeast, traveling down the valley; another says it came from the southwest. Along the railroad track from Gilroy to Sargent, nearing the fault, the intensity rose considerably, but the motion was a slow, swinging one. Water was all thrown from reservoirs, and trees swayed violently; but plastering and shelf goods suffered little. At Sargent all loose objects were thrown about, but no buildings were shifted. (A. J. Champreux.) — About 90 per cent of the chimneys in Gilroy fell, the prevailing direction being east and west. No frame houses were thrown off their foundations. Brick walls were damaged at the top by the fall of 8 to 20 courses of brick. Most of the plastered houses suffered by the cracking of plaster. No cracks were found in roads or pavements. At the Cemetery, about 50 per cent of the monuments were overthrown. Of the fallen ones, 95 per cent were thrown in an east-west direction. All monuments overthrown had square bases. Hollister to Priest ValleyHollister (G. A. Waring). — At Hollister (plate 114C, D) the chief damage was to the Grangers' Union, the Rochdale store, the Catholic school, and the fire-house. The two stores were poorly built, however, with large rooms unsupported by partitions or columns, while their shelves were heavily laden with goods. The school was on tall underpinning, very slightly braced, which allowed the building to lurch northward and settle to the ground. Unsupported parts of the fire-house walls (2 bricks thick) fell outward, but the portion braced by posts and tie-rods was unhurt. Sixty-five out of 123 chimneys fell, or 53 per cent. Several locked doors were thrown open, in one case the bolt being broken. One old settler remembers when the business part of Hollister was a slough. An artesian belt also passes thru the town, which may have affected the intensity along its path. (A. J. Champreux.) — Practically all chimneys fell, the prevailing direction being eastwest. One frame house, "School of the Sacred Heart," 2-story, was completely wrecked. The foundation gave way in the front part of the house, allowing the floor joists to drop. ― 289 ―
This house was on the outskirts of town and on sandy soil. No other frame house was damaged. Two brick buildings, of poor
construction, collapsed. The outer walls gave way, allowing the interior to drop.
(James Davis.)—Two shocks were felt, of which the second was the stronger. There was an interval of 3 or 4 seconds of less motion between these maxima. A rumble preceded the shock by a second or so. In my house a piano and other heavy objects were moved on a polished floor so that the north ends moved 2 or 3 feet out into the room farther than the south ends. I was standing at the time of the heaviest shock, and was thrown from side to side in a north and south direction. People here all agree as to the north and south direction of the movement. Most chimneys fell north, but some fell east and west. Pictures on east and west walls, hanging by single wires 4 to 6 feet long, swung from 3 to 8 feet along the walls, leaving distinct scratches. Pictures similarly hung on north and south walls simply pounded back and forth, leaving punctures in the plastering. Water-tanks seem to have fallen to the north always. Three brick buildings, each 2-story, 1 old and 2 new, went down flat, and 2 others were badly damaged. Wooden buildings in general were not damaged except thru the fall of chimneys. The Catholic convent, however, was injured. There were no changes in the ground at Hollister save some slight cracks in the vicinity; but a small peak near Santa Ana showed a landslide down its steep face, plainly visible at a distance of 6 miles. A huge rock, rolling down a hill in Santa Ana Valley, crashed thru a house and killed a man. (J. N. Thompson.)—All brick buildings were destroyed or badly damaged. There were 2 shocks, lasting in all about 50 seconds. The first appeared to be north and south, and the last part of the second shock appeared to be a twisting motion or a change to an east and west motion. My chimneys fell first, and nearly to the south; then at the last motion my wind-mill and tank fell to the west. The most damage was done at the close of the last vibration. A sideboard against a north wall was moved several inches to the south, and a clock on the same wall was thrown to the south. A bed against the west wall moved several inches to the east. From Hollister to San Benito (G. A. Waring). — The effect of the shock upon alluvial soil is very noticeable. In the hills toward the Stayton Mines the shock was so feeble that it was not noticed by some people. Thru Brown's, Los Muretos, and Quien Sabe Valleys it was generally only sufficient to throw the cream from pans of milk. The often repeated story of the man who was killed in Quien Sabe Valley, by a rolling boulder crushing his house, is not to be accepted as a measure of the intensity. Several loose rocks were shaken down in the neighborhood of Santa Ana peak, and springs increased their flow; nevertheless the shock was very light. At Palmtag's winery, in the hills southwest of Tres Pinos, the shock seems to have been more severe than elsewhere in the vicinity of that village. Furniture was moved, water was thrown from troughs, and an adobe building was badly cracked. One low brick winery was unharmed. A distinct rumble preceded the shock; 2 distinct periods were felt and the shock seemed very long. There is a small lake on the Palmtag place, and the ground seems rather marshy. Possibly this had some influence on the intensity, tho there is reason to believe that the projection of the fault passes thru the hills in the immediate vicinity. At Tres Pinos, out of 18 chimneys only one fell and it was unstable. Shelf goods were almost unaffected. There is hard rock (sandstone or shale) in place, however, at a depth of 2 to 4 feet, at Tres Pinos. Paicenes, tho south of Tres Pinos, was more violently shaken, for it stands on gravel. Milk and water were spilt somewhat, and a few tall bottles were thrown from the shelves. Water is said to have spouted up in the flat land along the river, 0.25 mile from the stream. ― 290 ―
Toward the Cienaga lime-kilns the intensity lessened considerably. One man in the foot-hills 4 miles southwest of Paicenes, reports seeing a wave coming westward thru a grainfield, and some oaks waving considerably; but he did not hear nor feel any shock. Four miles southwest of Paicenes, a hanging lamp swung strongly east and west, and milk was spilt from the pans. At the kilns, in a granitic region, tho a distinct noise is said to have preceded the shake, only one slight shock was felt, and that was not sufficient to spill water from a full bucket standing on a table. Along the river between Paicenes and Mulberry, a distinct vertical motion is reported, causing weighted windows to be thrown up and down, and stove-lids to dance about. Liquids were strongly affected, as were trees and hanging lamps, and a few articles were thrown from shelves. On the afternoon of June 13, a lady near Mulberry, 5 miles south of Paicenes, was talking over the telephone with a friend in Hollister. The latter suddenly gave a startled cry as a slight earthquake shock occurred. It was felt at Mulberry several seconds later. From Mulberry to San Benito the shock uniformly lessened until, at the latter place, altho distinctly felt, even liquids were not disturbed by it. Thru Bear Valley the only noticeable effects of the shock were the swinging of lamps and the disturbance of water surfaces. Little or no sound was heard in Bear Valley, but several people noticed 3 distinct periods of vibration. It began easily, rapidly increased, and then, after a pause, there came a harder shake. At one house a lamp hanging by a chain 3 feet long is said to have swung north and south nearly to the ceiling. Articles on shelves were not moved, nor loose window lights shaken out. At the summit at the south end of Bear Valley, about a bucketful of water was thrown from a barrel only two-thirds full, and cream was thrown north and south from pans of milk. Here also the hanging lamp swung strongly north and south. A man outdoors became dizzy and nauseated, but did not at the time realize the cause. Thru the south end of the valley, hanging lamps are said to have swung east and west, and water is said to have spilt mostly east and west. Several people became dizzy, but the motion seems to have been too slow to be distinctly appreciable. At the Pinnacles no loose rocks were displaced, so the movement must have been slight. Traveling southeastward from San Benito up the valley toward Hernandez, the motion consisted of longer, slower vibrations, and was of remarkably long duration. In general, the effect was only to set rocking-chairs in motion, cause doors to swing, and trees to sway. Just south of the divide between San Benito and Hernandez Valleys, the intensity rose noticeably, the shock throwing a lamp and clock from a shelf. At Hernandez, pans of milk and troughs of water were almost emptied, and many minor shocks have been felt since. No noise was heard before the quake, but a report as of a blast immediately preceded the second (hardest) period of vibration. This is in an upland valley at 2,500 feet elevation, but the ground seems to be full of water. In the mountainous serpentine area between Hernandez and New Idria, the shock was evidently slight, as nothing was noticed to have been disturbed at Smith's camp. At New Idria a few bottles and light articles were thrown from shelves, clocks were stopt, and a few bricks loosened from a building erected with mud mortar; but chimneys were not injured. One brick furnace was cracked, but it was not properly braced. Only 3 minor shocks have been noticed at New Idria. The intensity was about the same as at Hernandez. In Vallecitos Valley, at an elevation of 2,000 feet, Tertiary rocks are overlain by 50 feet or more of alluvium. In this valley, pans of milk were slightly spilt, but nothing was thrown from shelves. From San Benito southward thru the Bitterwater Valley, the intensity lessened, and only liquids were affected. The motion was too slight to be appreciable to some people. ― 291 ―
Priest Valley (D. S. Jordan). — On May 18 I went to Priest Valley, in the southeast corner of Monterey County, 37 miles east of King City. I had heard that rumblings were frequently heard in the valley, and that people were moving out on account of them. There was little trace of the earthquake at King City. At Lonoak, 16 miles east, chimneys were thrown down and a mild earthquake was felt. At Priest Valley, which is near the line of the old fault and at the very foot of the main range of the Gavilan, the earthquake shock was very severe, apparently coming from the north. Chimneys were thrown down, dishes were broken, and the contents of the store thrown over the floor. Rumblings were alleged to have been heard by a man named George Brew. He had been hunting in the mountains, and said he had heard noises like cannonading in the ground at night. This was before the great shock. There were slight landslides and cracks along the edge of the creek banks. There is, however, no trace of the great crack in the valley. No one had seen it cross the stage road; and the oil pipe line from Alcalde, in Fresno County, goes thru to the Salinas Valley without any break. The people said to be moving out of the valley were two frightened women up in a mountain gorge, whose husbands had gone to look after friends in San Jose. It is evident that the main crack did not reach as far as Priest Valley, and the shock at that point was not very different from that at San Jose, except that the blow was more direct, with less twisting motion. Monterey Bay and EastwardPacific Grove, Monterey, and Del Monte (A. S. Eakle). — At Pacific Grove very slight damage resulted from the shock, altho according to residents the vibrations were very severe, in a northeast to southwest direction. Only one or two houses had chimneys cracked, tho there are several massive chimneys, some with heavy ornamental tops. The town is situated on massive porphyritic granite, and the overlying soil is not deep. Its situation was evidently the reason for the slight damage done. The Pacific Grove light-house is situated about a mile southwest and this showed more severe effects. The lamp is enclosed in a ribbed metal frame which rests on a brick tower and dome. The vibration of the ribs caused them to strike the metal chimney in the center of the top and dent it on the easterly side. The motion of this upper portion caused the brick dome supporting it to crack immediately at the base of the curved dome. There was no displacement of bricks, the crack being a fine one, visible both within and without the tower, and completely encircling it. The light-house is built on a sand-dune and there is an estimated thickness of 80 feet of sand upon the underlying rocks. This sand foundation probably accounts for the apparently greater intensity of the shock here than in the town. Some of the objects in the rooms of the house were also slightly misplaced. Judging the intensity of the earthquake by the damage it did in Pacific Grove, it would probably be classed as VI in the Rossi-Forel scale, as it was severe enough to awaken practically every one, tho no windows were broken, so far as could be ascertained. Monterey experienced practically the same intensity. I could learn of no damage done to the houses, the only damage reported being of some glassware in a few stores. In some houses furniture was moved slightly, and top-heavy pieces were overturned. This town, like Pacific Grove, is on a good rock foundation; but in places the sand is deep. Del Monte suffered the most, as practically every chimney of the hotel was cracked or thrown. There were over 50 chimneys in the hotel, and half of them were thrown down, one crashing thru the roof on the west side of the hotel and causing two fatalities. The chimneys were tall and top-heavy, having ornamental tops; and while the damage to the interior of the hotel was very slight, showing that the earthquake was not of a violent type, the vibrations were sufficient to throw these top-heavy chimneys. The hotel is on ― 292 ―
alluvium, and the grounds surrounding it are in part "made" land. The grounds are surrounded by marshy land, ponds, and sand-dunes,
and there is evidently a considerable depth of an incoherent, water-saturated formation supporting the hotel; this probably
explains why Del Monte suffered so much more than Monterey. The houses adjoining the grounds were not damaged, with the exception
of the school-house, which had its chimney cracked at the base.
On the road eastward to Salinas from Del Monte, no visible signs of the earthquake were encountered until the Salinas River was reached. The Salinas bridge was moved southerly several feet, according to report, and the framework was broken so as to render the bridge unsafe. The bridge farther down the stream, on a wagon road from Catroville railroad station to Monterey, was also damaged by the shock. This bridge crosses the river in a northeast to southwest direction, and is supported by four tiers of piles, boxed around with plank. The two end piers were not misplaced, but the two intermediate series were bent or broken at their bases and shoved over to the northeast, causing a sinking in the center of the bridge of about 2 feet. The damage to the bridge was due to the violence of the shock, and not to a sinking of the ground, as the amount of drop in the center was equivalent to the slanting position of the two intermediate supports. Castroville to Soquel (G. A. Waring). — Castroville, being on solid ground, was not seriously affected. Three chimneys out of about 30 fell. Objects were thrown mostly westward. The quake was described as beginning like a subterranean blast. Two periods were not noticed; it was felt as one continual vibration, starting very gently. The wharf at Moss Landing buckled up and partly collapsed, while the warehouses were wracked or fell westward. (Plate 116D.) At the hotel and stores on the mainland, brick chimneys fell, but plastering was not seriously cracked. At Watsonville about 90 per cent of the chimneys were broken off at the roof-line, the greater portion being near to the river. Several were cracked and twisted but not thrown down. Parts of a few brick walls near the river fell, and considerable settling of the ground took place in Chinatown on the southern side of the river. (Plate 116A.) On the higher ground between Watsonville and Aptos, the shock was little felt. There was no movement along Aptos Creek, both wagon and railway bridges being unaffected. In one old house about half the plaster was thrown from every northern and southern wall on the first floor, but not from the others, nor from the upper rooms. A bureau was moved eastward 3 feet from the wall, but no other furniture was moved. Nearly all the chimneys at Capitola fell, and considerable plaster was shaken from the north walls of the first floor of the hotel. The vibration is said to have been almost entirely east and west, as shown by the sash locks having been broken only upon the east and west windows. An iron safe free to move northward was unmoved, but the plaster on the opposite side of the wall back of it (west) was broken. A case of pigeon-holes resting on top of the safe slid to the east edge, when it could as easily have moved north. Much earth fell from bluffs near the town, but there was no appreciable effect on the surf. At the country bridge across Soquel Creek, the ground at the east abutment shoved inward, cracking the concrete and buckling a water-pipe. In the low ground at Soquel, nearly all the chimneys fell, but most of those on high ground stood. Much plaster fell and goods were thrown from the shelves in the business section, which is close to the creek. The east abutment of the concrete wagon bridge over Soquel Creek cracked vertically, showing that the soil movement extended this far up the creek. Thru Delmar, Seabright, and Twin Lakes nearly all the chimneys were either down or twisted part way around and left standing, an unusual number being thus twisted. The shock is said to have come suddenly, diminished, and then, at a second jolt, chimneys fell. Trees moved sideways as well as swayed, and all animals were much frightened. One small stream has diminished in flow. ― 293 ―
(D. Stirling.)—In the Pajaro Valley, on the McGowan ranch, at a bend of the river, an acre or more of orchard has sunk about 2 feet. At Moss Landing, where the river runs parallel with the shore line, the strip of land is seamed for miles. A crack, or rather a sink, about 20 feet wide and 4 or 5 feet deep ran under the buildings and rent them asunder. The office building between this crack and the river has been moved bodily — land and all — about 12 feet toward the river. Some of the cracks run into the ocean. At Neponset and Salinas the piling under the county bridges was moved in some of the bents at least 10 feet toward the river. A section man who stood in the midst of the cracks at the end of the Neponset bridge was drenched with spurting water. Salinas to San Luis Obispo and WestwardEffect of the Shock on Alluvium (G. A. Waring). — Altho the Salinas river bed sank nearly 6 feet at King City, and the wide sandy bottom at Three Mile Flat was much cracked, the southernmost extension of continuous cracks along the bank was found to be about 2.5 miles south of Gonzales bridge. From here to the mouth of the river the cracks are parallel with the river banks. The movement at Gonzales bridge was mostly on the west bank of the stream. A wire fence trending north and south was torn 6 inches apart here, and wooden piles at the southwest end of the bridge, said to be driven down 75 feet, have been torn loose and moved from plumb, their original upright position. At the northeast end of the bridge the piles are undisturbed, but the surface soil and a wire fence have moved relatively 18 inches northward. (See fig. 59.) North of Gonzales bridge the fissures are mostly on the west side of the stream channel, and reach a maximum width of 18 inches. No evidence of shearing could be found. In the creek bottoms west of Chualar, sand craterlets begin to appear and become numerous along the stream northward. Near Agenda, in the lowlands, is a cracked area nearly a mile from the river, probably along an old water course; while sand craterlets are scattered thru the orchards. At Spreckels the movement caused much damage to flumes, sewers, and water-mains; and from here to Blanco the deep soil of the adjacent fields is much cracked and in places sunken and dotted with sand craterlets. The county bridge south of Salinas was rendered unsafe by the movement of the piers at the southern end. (Plate 123A.) On the west bank near the bridge a series of peculiar cracks have torn up the road and adjacent field, along what is probably the path of an old water course. These are shown in plates 136, 137. Between Blanco and Neponset the cracking and settling of the low land flooded the adjacent fields and gave rise to stories about the Salinas River having risen several feet. The "boiling up" of the water thru sand craterlets was also soon distorted into a story about the water of the Salinas River being boiling hot. Both the railway and county bridges at Neponset were moved, the northern concrete piers of the former 2 inches east and the central wooden pier of the latter apparently 4 feet south. From Morocoho to Moss Landing fissures rarely show in marshy land, but the narrowgage railway track has been shifted a few inches in several places. At Moss Landing many small cracks occur in the mud on the west side of the river, and the condition of the wharf indicates an eastward movement of the sand-spit. (See plates 134B, 135A, B.) It is reported that at places along the pier where the water was formerly 6 feet deep, it now has a depth of 18 or 20 feet. North of Moss Landing the ground settled nearly 2 feet in places, as shown by marks on railway piles at several slough crossings and by the sagging of the track below grade line in several other places. The stretch of narrow-gage track parallel to the coast has been disturbed for nearly its whole length; in some places it is wavy, in others the entire roadbed has shifted. At one point about 5 miles south of ― 294 ―
Watsonville, where the railroad track is only about 200 yards from the beach, a stretch 100 yards long running northwesterly
had shifted a maximum of 12 feet to the northeast. Fences, telephone poles, and track all moved together. The sand-dunes facing
the beach directly opposite the place where this movement occurred look as if they had been struck by a single large wave.
Cracks appear again along the Pajaro River and the railway track has sunk in several places. The side rods of the narrow-gage bridge 1 mile south of Watsonville are buckled as by a compressive force, and the roadbed at both approaches has settled at least 2 inches. Continuing up the Pajaro River, evidence of settling is found at the broad-gage railway bridge at Watsonville, the southeast end of which sank more than a foot. The track was also twisted into an S-shape. The concrete foundation under the engine and stack at the power-house at the northwest end of the bridge settled, but the concrete work was little hurt. In Chinatown, on the south side of the river, the settling of the ground was marked. Between Pajaro and Vega the ground cracked along the 2 to 6 foot bluff, marking the old river bank on the south side of the present channel, and the side toward the river has settled several feet. This is well shown in plate 141B. This displacement has caused numerous sand craterlets and pits (plate 143B); the largest pit noted being oval in shape, 6 by 20 feet in diameter, and 4 feet deep. Northeast of Vega the movement seems to have died out, the last evidence found being mud caps on some old piles in the channel of the stream, showing a settlement of the ground amounting to 8 inches. Between Vega and Chittenden no evidence of movement of the river-bed could be found. Near Chittenden the banks are caved in. Along the San Lorenzo River, at Santa Cruz, this settling action also took place for a mile or more upstream from its mouth. It may be said, regarding the soil movement along these streams, that along the Salinas River from Gonzales to near Blanco, everything shows a movement down the river. From Blanco to Neponset the movement seems to have been a settling of the alluvial materials, while from Neponset to the mouth of the Pajaro River the ground (in several places, at least) moved eastward or inland. Accepting as correct the reported lengths of piling at bridges, and depths at which the sand thrown up is said to have been found, the plane of movement must have been about 90 feet below the surface at Neponset, diminishing to possibly 8 or ― 295 ―
10 feet at Gonzales bridge and ending about 2.5 miles south of it. Along the Pajaro and San Lorenzo Rivers the movement was
a settling of the alluvial bottom-lands.
(A. S. Eakle.) — The effect of the earthquake upon the alluvium was well shown along the banks of the stream from the Salinas to the Gonzales bridges. Along the east side of the river for a short distance south of the Salinas bridge, 4 miles south of the town, the land is cracked at the edge of the bank, the cracks paralleling the course of the river; but comparatively little cracking was observed on this side of the river. Along the bank and down in the river-bottom itself, on the western side of the stream, fissures were very prominent. The county road southward from the Salinas bridge runs along the embankment about 10 to 20 feet above the stream bed. The road is an oiled one, and the oil had formed a hardpan upon the underlying sand. In the vicinity of the bridge the road has been shattered by the quake for a distance of 200 yards. The breaks are in the nature of a caving in of the road on the north side of the crack, as if hollow spaces existed beneath, leaving a vertical escarpment on the south side. The main sinking is at the most southerly fissure. Here the road has sunk bodily to a depth of 10 feet, leaving a high vertical bank diagonally across the road, and this sunken area extends for some distance into the adjoining field on the west. There is no upheaval of the road in any place to compensate for the sinking. South of the Spreckels factory, the low bottom-land between the banks of the river is considerably cracked, although there is no prominent vertical dropping of the land along the cracks. This low land lies west of the present course of the stream, and is intersected by sloughs and former water courses. All of the ground is of a deep sandy nature, consequently it was much disturbed and fissured by the quake, and the fissures became filled with water and sand, forming a quicksand, this wet sand frequently being spouted into the air. No one noticed gases coming up. The position of the cracks is now marked by patches of light, bluish-gray sand in the field, from the drying out of the quicksands. Houses on this low land were thrown out of plumb, and chimneys were destroyed. The cracks diminish in number as one goes southward, and practically end in the vicinity of the Gonzales bridge. The quake at Gonzales can hardly be placed at more than VII in the scale, as comparatively little damage was done to the town. Effect upon structures, objects, etc. (G. A. Waring). — It is remarkable how closely the disturbance followed the river channel throughout the Salinas Valley; 2 or 3 miles away from the stream on both sides the intensity was very slight. Southward up the valley the shock gradually lessened, and rapidly died out in the foot-hills on either side. In the hills between San Juan and Natividad the ground is not cracked, except for a few places on hillsides where there was some sloughing off. The shock was sufficient to throw nearly all the milk from the pans, but not strong enough to move furniture or shelf goods. At Natividad, in the foot-hills, the shock was of about the same intensity. At Santa Rita the shock was light; a little milk was spilt from pans, but several tall slender chimneys were unhurt. Prunedale (H. H. McIntyre). — Nearly every chimney was thrown down. All the goods in the store were thrown to the floor. The house was badly wrecked. Water started flowing in many places where there had been none, or but little, before. There were 2 small landslides from springy places, the direction of the slip being from north to south. Salinas (G. A. Waring). — At Salinas 42½ per cent (278 out of 655) of the chimneys fell. A brick store was demolished by the collapse of the roof (plates 115B, 116B), and parts of a dozen or more brick walls fell. (Plate 116C.) Shelf goods were shaken down, and a few heavy articles, such as slot machines, were overturned. Heavy furniture, such as pianos and billiard tables, was not moved. But little plate glass was broken. In ― 296 ―
some buildings plastering was badly cracked and shaken down, but in solid, well-built residences it was little hurt. The court-house
and high-school buildings, within a block of each other, furnish striking examples of the need of considering construction
when trying to gage the intensity of the shock by its effect on buildings. In the former building the principal damage consists
of a few cracks in the plastering and foundations, while in the high-school building a part of the front wall fell out and
the roof spread badly, cracking the corners of the house.
(A. S. Eakle.)—The town of Salinas suffered greater destruction than any other place in the county. Nearly every house and building were damaged to some extent. Plaster fell, windows broke, chimneys fell or were cracked, and brick buildings had their upper portions thrown off and, in some cases, almost completely demolished. The town is on the flat valley land, about 3 miles east of the river, and came within range of the more violent vibrations, in addition to being on alluvium. Spreckels and vicinity (G. A. Waring). — The village of Spreckels, on the river-bottom, was badly shaken. Nearly every one of the approximately 50 chimneys in the settlement fell, as did also a large part of the plaster in the 3-story hotel. On the first floor of the hotel building nearly all the walls were stript, but the plaster fell mostly from the south wall. On the second floor the walls of the north end and west side suffered most, while on the third floor the north end (walls and ceiling) was shaken the hardest. In the 6-story, steel frame, brick sugar mill (plate 117A, B) the bricks along the I-beams of the north end were thrown out, as were also those of the upper central part of the west wall, and part of the top cornices of the north and south ends. Oil in a large tank was thrown toward the southeast. The front (north end) of the 2-story brick office building exhibits a remarkably symmetrical set of cracks. (A. C. Lawson.)—The flood plain of the Salinas River was caused to lurch toward the stream from both sides, but the effects are most marked on the south side. The result in most places has been the breaking up of the alluvium into monoclinal strips with a vertical scarp on one side, facing the river, and a gentle slope on the other. These have the effect of landslide scarps and terraces, but occur on flat land. In some instances it would appear that the ground had collapsed into the cavity formed by the lurching. There are minor cracks and buckles in the sand and mud flats of the river-bottom. Here numerous craterlets were formed by the sudden ejection of water from the underlying sands, due to the compressive action of the shock. This acute deformation of the ground accentuated the destructive tendency due to the earthquake shock. At the bridge, a large trussed structure in 2 spans having a bearing of N. 27° E., the south pier, consisting of 26 piles incased in planking, was thrust to the south between 6 and 7 feet, so that the entire pier was inclined as shown in plate 123A. The piles were not broken at the ground level. The north and middle piers were apparently not affected. An oil pipe which crost the bridge was buckled and twisted at the south end of the bridge, and when this was repaired the pipe was found to have been shortened 7 feet. The pipe line extends from the San Joaquin Valley to the Bay of Monterey. A few hundred yards to the south of the bridge is a pumping station, and at this point some of the connections of the pipes were broken and displaced. The direction of the shortening of the bridge span and the pipe is roughly normal to the direction of the San Andreas Rift, on the other side of the Gavilan Range. Mr. S. A. Guiberson, superintendent of the line, reports that the pipe was broken in about twenty places in the vicinity of the river, and that at some of these breaks the pipe was pulled apart. A few hundred yards east of the bridge, on the south side of the Salinas River, is the Spreckels sugar-mill, a steel structure incased in brick, about 500 feet long and about 150 feet wide, having a northeasterly and southwesterly orientation. This building is five stories high, but the five stories occur only at the two ends of the building. In ― 297 ―
the middle 100 feet of its length there is only one floor above the ground-level, and above this the structure is open to
the roof, without cross-ties or floor-beams. This building yielded to the shock in a most remarkable and instructive manner.
The whole structure was shortened along the line of its longer axis, this shortening being effected by the buckling of the
walls at the middle or weak portion of the building. Both walls bulged toward the west, the east wall in and the west wall
out, as shown in plate 117A, B. Within the building considerable damage was done to the heavy machinery, tanks, etc. The ground
to the south had been much heaved and otherwise deformed, causing the wrecking of trestles, pumping-house, and other structures.
The rails of a track at the rear of the building were pulled apart, due probably to the slumping of the ground toward an old
slough of the river.
In the bottom of this slough water gushed forth at numerous places at the time of the earthquake. It is said by those who witnessed the phenomenon that the water spurted repeatedly as high as 20 feet, and that the outflow of water lasted for 10 minutes after the shock. The places where the water spurted forth are marked by areas of fine, light, bluish-gray sand, which is said to be known only at a depth of 80 feet in the various well borings of the vicinity. In these areas of fine bluish sand are often funnel-shaped depressions or craterlets from which the water issued. (S. A. Guiberson, Jr.) — As superintendent of the pipe line, I am in a position to say that we have no breaks whatever in any place between Coalinga and the Salinas River, and there were no fissures of any kind along the line between these points. This I know positively, as I have line riders who were instructed to look closely for any disturbance of this nature. The line of fissures seems to have ended north of Priest Valley. The conditions prevailing along the Salinas River, and some of the peculiar circumstances attending the breaking of our line in about twenty places, are of interest. I was on the ground the following day, and only regret that I did not have time to have some of the peculiar features photographed. In places our line had been broken and the ends were 3 feet apart; at the same time the ends of the pipe would be hammered up, showing that there had been an opening and closing movement at that point, while at other points the line would overlap as much as 4 feet. One of our stations is in this zone of disturbance, and the engineers, being on duty, had an excellent opportunity to see what most of us who were in bed merely felt. They state that these fissures were opening and closing, and that the water and sand would go 20 feet in the air as they closed. Southward from Salinas (G. A. Waring). — At points along the railroad liquids were generally spilt, furniture was moved, and chimneys cracked. At Chualar, 3 out of 29 chimneys fell, but 2 were on an old house and were probably weak. At Gonzales the intensity seems to have been about the same as at Chualar. Out of 150 chimneys 11 fell, while many were cracked. East of Gonzales, near the foot-hills, houses were barely shaken; while to the west, near the river, water-tanks were thrown down. At Soledad 3 out of 8 chimneys fell, but the number is probably too small to be taken as a criterion of intensity. Some plastering on the first floor of the hotel was slightly cracked, a few glasses were thrown from the bar, and some of the bottles were turned around. The frame of the railroad tank was so badly twisted that it had to be taken down. A chandelier swung northeast-southwest with a double amplitude of 18 inches. At King City, close to the river and on low ground, the intensity was considerably higher than at Soledad. Heavy objects, such as a printing-press, slot machines, and ice-chests, were shifted a little, and a few things were thrown from the shelves. One low chimney on a low fire-wall fell, but the wall was without a crack. No other chimneys were injured. The river-bed sank nearly 6 feet in the vicinity of King City. At San Lucas the intensity was considerably lower; milk and water were spilt and shelf goods disturbed, but no chimneys fell. ― 298 ―
On the western side of the valley from Salinas to San Lucas the same kind of evidence was found as at corresponding points on the eastern side. At Fort Romie most of the clocks stopt, a few articles were thrown from the store shelves, and water in a north and south canal was thrown over the sides. No sound was heard during the shake, but it is reported to have come afterward. About 4 miles south of Fort Romie, water was thrown 30 feet northward from a full tank, the top of which is 14 feet above the ground, and half the milk was thrown from half-filled pans. West of San Lucas, waves were reported to have been seen moving southward over the hills and a sound to have been heard. The shock began gently, was followed by a harder shake, and died away slowly. Thru San Ardo, Bradley, and San Miguel, the shock lessened uniformly. At San Ardo a water-tank frame was somewhat wrenched, and the river-bed is thought to have sunk about 2.5 feet, tho evidence of this was not obtained. Oil was spilt from a large tank, and quicksand was thrown up in a well, which seemed to lessen the flow considerably. The railway station at Bradley, standing on made ground, settled 2 inches at one end. At Paso Robles a number of clocks were stopt, most of which were facing east or west. Window weights rattled and lamps swung about, but plastering and shelf goods were not affected. The duration of the shock was estimated at 40 seconds, but was very gentle. In the southeastern end of the Salinas River drainage area, at Shandon, Cholame, and Parkfield, the shock was notable as being "the longest, easiest one felt in many years"; liquid surfaces were somewhat disturbed, a few clocks were stopt, and hanging objects were set in motion. In the hills 2 miles northwest of Shandon the intensity was somewhat greater, as it was also to the southeast in the Red Hills. At Shandon, a saddle hanging by a wire from the rafters swung north and south, and water was thrown from a full horse-trough. The shock was also reported at Estrella and Linne. South and West of Salinas Valley (G. A. Waring). — Following southward over the divide thru Templeton, Santa Margarita, Dove, and Guesta the shock lessened until it was hardly more than distinctly felt. At Templeton skimmed milk was spilt at one place, but unskimmed milk was not. At Dove the swaying of the telegraph wires was about the only evidence noticed. At one place a mile east of San Luis Obispo a great roar is reported to have been heard. In the coastal range of hills thru Carmel P.O., Jamesburgh, and Jolon, only milk and water were disturbed, but from the latter place to Los Osos Valley, west of San Luis Obispo, the shock varied considerably. At Lockwood the shock was a little stronger than at Jolon, clocks being stopt generally and milk and water spilt, but no shelf goods were moved. Thru Hames and Pleyto it hardly more than wakened sleepers, and people moving around did not feel it; while at Adelaide clocks were stopt, shelf goods moved, and liquids spilt. Several minor shocks have also been felt at Adelaide. In Los Osos Valley, however, the shock was barely felt; sound sleepers were not awakened. A few light things, such as table covers, swayed slightly, but no sound was heard, and pans of milk were undisturbed. At San Luis Obispo the shock was hard enough to waken all ordinary sleepers. Some people thought it a wind-storm. The vibration is estimated by some to have lasted 20 seconds. Mr. John R. Williams states that the shock made doors and windows rattle, moved his bed, and stopt some clocks. There was but one principal disturbance, which gradually increased in intensity and then died away, lasting about 50 seconds. The apparent direction of movement was northeast and southwest. The night operator at the telephone office was talking with Salinas at the time the shock occurred. She heard a scream at the Salinas end, followed by a roaring sound. Fully half a minute later the shock was felt by her at San Luis Obispo. ― 299 ―
Along the coast northward from Port Harford thru Morro, Cayucas, and Cambria, to San Simeon, the intensity gradually rose. At Morro some people in bed and awake felt it; many others did not; while at San Simeon liquids were somewhat disturbed and the shock of the afternoon (of April 18) was also noticed, which was not the case farther south. At Piedras Blancas Light-house a clock stopt and the shock was distinctly felt. Between San Simeon and Posts the country is almost uninhabited, and not easily accessible, so it was not visited. At Posts a clock was stopt. The shock was very appreciable, and several minor ones have been felt since. At Idlewild several articles were thrown from shelves, windows rattled, and the redwoods swayed considerably. At Sur a clock was stopt and the shock was apparently a little stronger. At Carmel-by-the-Sea, on deep, sandy soil, several people ran out of doors, a cobble-stone chimney fell, and a few tall articles were tipt from shelves. San Luis Obispo to San BernadinoThis portion of the state is on the southern fringe of the region within which the shock appealed to the senses. The shock was not exceptional in intensity and the people paid little attention to it; therefore records of observations as to the effects produced are few. Such reports as have come in, however, indicate that the shock was more or less distinctly felt thruout the country north of the Santa Barbara Channel and the Valley of Southern California, as far east as San Bernardino. Arroyo Grande, San Luis Obispo County (G. P. Ide). — Pendulum clocks facing north and south were stopt, while those facing east and west were not. Very few objects were overthrown. A hanging object swung east and west in an elliptical orbit. Other points south of the town of San Luis Obispo at which the shock was reported are:
Santa Maria, Santa Barbara County (F. R. Schank). — I was asleep in the second story of a brick building and was awakened by the first of 3 shocks. The shock awoke people generally and was observed by persons moving about, but did no damage. The motion was a slow, easy one. Wooden inside shutters at my windows swung thru a considerable arc, and an incandescent lamp suspended by about 5 feet of cord vibrated with an amplitude of about 6 or 7 inches in a plane approximately east-northeast. The length of the first and second shocks was 1 or 2 seconds, but the third shock lasted between 12 and 15 seconds. Casmalia, Santa Barbara County (C. H. Stephens). — I was awakened by the jar, and the rocking was continued for about a minute, when all became quiet. It then started again lightly, getting stronger as it proceeded and gradually dying away in about 45 seconds. The third shock came quite strong, and 6 waves followed close on each other, each stronger than the preceding one. The clock was stopt, and some articles of furniture were overturned. Surf. — A clock was stopt. Lompoc, Santa Barbara County (C. K. Studley). — I was in bed, awakened by the first slight trembling. My bed stands east and west, with the head to the west. The first shock moved me up and down from head to foot. The second shock rolled me from side to side. The first shock gradually increased to a maximum, and then died out; the second seemed to be about the same intensity thruout, and stopt suddenly. The latter set the window weights on the south side of the house rattling quite rapidly. The hanging lamp suspended from the ceiling of the lower story by a chain, which would make it about equal to a pendulum that beats seconds, swung in an elliptical orbit, the longer ― 300 ―
diameter being 10 inches in a west-northwest direction and the shorter diameter 4 inches in a north-northeast direction. The
motion in the ellipse was clockwise. The clock stopt.
Point Conception Light-house Station (Mr. Austin). — While cleaning up in the tower at 5h 20m A.M., the keeper felt the lens shake. No one else at the station felt the shock. Santa Barbara (J. A. Dodge). — I was aroused from a half-sleeping condition by a singular rustling noise in the house. None of us recognized it as an earthquake at the time. My bed was not perceptibly shaken. Nothing was shaken out of place, no plastering was cracked, and no clocks were affected. The sound referred to was produced by something in the structure of the house creaking or vibrating. Other reports state that some hanging objects were caused to swing, and that one woman was made dizzy. Carpenteria, Santa Barbara County. — The shock was sufficient to rattle dishes and slightly move beds, but few people were awakened by it. Saticoy, Ventura County (E. O. Tucker). — Water in a trough which was 6 inches from being full, slopt over nearly a pailful at a time from the ends. The trough lies from northeast to southwest. A rattling noise was heard in the house, but no motion was felt. Hueneme Light-house Station, Ventura County (C. F. Allen). — The earthquake was one abrupt shake which gradually died out, lasting 4 seconds in all. The weight to the clockwork which turns the light thumped back and forth in the weight-well from northwest to southeast, and the window weights did likewise. In Ventura County a slight shock was reported at Newberry Park, Punta Gorda, and Ventura. At the latter place, hanging objects were observed to sway from east to west. Calabassas (H. H. Wheeler). — A farmer stated that a number of cisterns for collecting rain-water for domestic uses were cracked by the earthquake shock so that they leaked. Santa Monica, Los Angeles County (T. H. Moody). — A disturbance was noticed which seemed to be on the front porch, the noise continuing with considerable regularity, and appearing to change from place to place. Then there was other cracking around the house, and finally all was quiet. Nothing moved out of place. Los Angeles (J. D. Hooker). — There was a light shock, then a heavier; then a smart shock which caused windows and doors to rattle. A window curtain swung in and out. A brass ring attached to a cord 15 inches long swung northwest and southeast. At the Weather Bureau station the barometers were observed to swing and rattle against the rings which confined them. The shock was also reported as a slight one at Azusa, Claremont, and Toluca, in Los Angeles County. Anaheim, Orange County (J. F. Walker). — Very few people in Anaheim report having felt a shock at all. It was very slight. No clocks were stopt. San Bernardino (Dr. A. K. Johnson). — The shock was sufficient to stop the town clock at 5h 17m, and several persons felt the vibrations, but no movable objects were displaced. At 4h 30m P.M., April 18, a slight oscillation was felt which caused the chandelier to sway. This movement continued for a few seconds, and seemed to be from northwest to southeast. Bay of San Francisco to the San Joaquin ValleyIn Contra Costa and Alameda Counties the destructive effects of the earthquake were most manifest in the cities of Berkeley, Oakland, and Alameda, on the east side of the Bay of San Francisco. Berkeley (A. C. Lawson). — A large majority of the brick chimneys were broken or overthrown, and in addition to this several brick buildings had their upper walls thrown down or were otherwise damaged by cracks. The most notable cases of this kind of damage indicative of the intensity of the shock may be briefly mentioned. At the State Institution for the Deaf, Dumb, and Blind the upper part of the northwest tower of the building, to the north of the central structure, was wrecked by a considerable ― 301 ―
part of the brickwork being thrown out on the northeast and northwest corners of the tower. (Plate 118B.) The upper part of
a brick gable in the central building, facing northerly, was thrown southerly, or into the building. The upper part of the
tower on the northwest corner of the building to the south of the central structure was demolished. (Plate 118A.) The main
clock tower of the Institution, however, suffered no serious damage. The clock, a very unreliable one, stopt at about 5h 13m. At the High School the walls of the upper story, particularly those facing west, were badly cracked and partly thrown out,
so that they had to be taken down. Two large brick chimneys on the east roof collapsed and did much damage to the rooms below.
(Plate 119B.)
The Barker Block, at the northwest corner of Shattuck Avenue and Dwight Way, a building veneered in part with brick, had a great deal of the brick facing of the upper part of the building, and much of a strip of tiling above the east wall, thrown down. (Plate 119A.) The upper part of the rear wall of the brick building at the northeast corner of the same streets was thrown down. The north wall of the new Masonic Temple, which was in course of construction at the corner of Shattuck Avenue and Bancroft Way, was thrown to the north and caused the collapse of certain steel girders resting upon it. The intensity of the earthquake within the city of Berkeley was by no means uniform. There were areas which seemed to a very considerable extent to be immune to the destruction so marked in the throw of chimneys, etc., in neighboring areas. The buildings on the University campus, for example, sustained no serious damage, and there was not a single chimney thrown, altho one or two were cracked. In a belt of the city extending northwesterly from the vicinity of the President's residence on the campus, the damage to chimneys was similarly light. This comparative immunity to destructive shock appears to be associated with the fact that the buildings on the campus, and in the belt to the northwest of it, are practically founded on rock, whereas the portion of the city where chimneys generally fell is on alluvium. The direction of the fall of chimneys at Berkeley, as elsewhere, was controlled to a large extent by the orientation of the houses. Chimneys usually fell nearly at right angles to the longer side of their cross-section, which was as a rule parallel to one of the walls of the house. Notwithstanding this fact, however, there was a prevailing tendency in the fall of chimneys to the south and east, or in the southeast quadrant. Where chimneys fell to the east, they fell usually a little to the south of the line at right angles to the north and south wall; and where they fell south they fell similarly a little to the east of the normal to the east and west wall. Some square chimneys fell diagonally to the southeast. This was true of a rather massive 4-flue chimney on the writer's house, which fell at the latter end of the shock. In many cases chimneys were dislocated and twisted, without being thrown down. Of 38 chimneys, the rotation of which was noted by observers giving their entire attention to the matter for the time being, 31 were rotated counter-clockwise and 7 were rotated clockwise. In some parts of Berkeley the rocking of the houses was sufficiently violent to make it difficult, and in some cases almost impossible, to stand on the floor without support. According to the observations of the writer, there were two maxima in the shock, with a lull in the interval, the second being the more violent. The movement appeared to be diagonal to the rectangle of his house, the longer side of which is approximately east and west. The throw of objects was much more to the west than to the east. This was well exemplified by the behavior of objects in the mineralogical museum on the third floor of South Hall. These are upright cases reposing on cabinets of drawers. The shelves, arranged in steps, are orientated north and south approximately, and face both east and west. On the shelves facing east very little was disturbed, while in those facing west ― 302 ―
many of the heavier specimens, weighing 20 pounds or more, were projected from the largest, or top shelf, thru the glass doors,
and were found strewn on the floor. In no case, however, was the glass of the doors broken. The latter had been forced open
at the same moment that the masses of rock had been hurled toward them, thus allowing the missiles to pass thru. Smaller specimens,
weighing less than a pound, on the shelves immediately below the top one, were very little disturbed.
Oakland (A. C. Lawson). — The destructive effects of the earthquake were much more in evidence in Oakland than in Berkeley, and this is doubtless due in large measure to the much greater number of brick and masonry structures susceptible to this kind of damage. When particular instances are considered, however, it seems probable that the severity of the shock was in reality somewhat greater in Oakland than in Berkeley. Chimneys fell very generally thruout the city; the upper parts of brick walls, gables, and cornices were in many cases thrown down (plate 122B) and cracks in walls were numerous. The underpinning of some few old frame houses caused these structures to collapse. In addition to this damage, which indicates fairly well the prevailing intensity of the shock, there were several cases of more severe destruction which must be noted. The Prescott school, in course of erection, at the corner of Ninth and Campbell Streets, was rather badly wrecked (plate 121B), as was also the building of the California Flax Works, on the corner of Union and Third Streets, the walls of which gave way, causing the roof to collapse. (Plate 121A.) The susceptibility of this building to destruction was probably due to lack of transverse bracing for the walls, except that supplied by the roof girders. The southeast tower of the First Baptist Church, on Telegraph Avenue, had its upper northeast corner thrown out, and was otherwise wrecked. (Plate 122A.) The east and south gables were both thrown out; but the lower towers at the northeast and southwest corners of the building were comparatively unaffected. The Central Bank building, at the corner of Fourteenth Street and Broadway, had the brickwork of its southwest corner thrown off from the 2 upper stories, and was similarly affected, tho to a less extent, on its northwest corner. (Plate 120A.) The large smoke-stack at the Key Route power generating plant, built on the tidal marsh land, had its upper third thrown off. (Plate 120B.) Considerable damage was also done to the First Unitarian Church, at the corner of Castro and Fourteenth Streets, and to the Christian Science Church, at Franklin and Seventeenth Streets. (E. C. Jones.) — There were very few breaks in cast-iron gas-mains. Two of these were caused by impact of heavy débris falling from buildings and poles. One was on Washington Street, where heavy blocks of sandstone fell from the third story and the roof, breaking the main 30 inches below the bituminous rock. Another was at the corner of Fourteenth Street and Broadway, where a transformer fell from a pole, striking the center of a short car rail and bending up both ends. A 3-inch cast-iron main a short distance from this was broken at right angles. On the Twelfth Street dam, a cast-iron pipe was broken and displaced over a foot; while the high pressure steel pipe paralleling it was practically undisturbed. Gas-holders were uninjured, tho much of the water was thrown out of the holder tanks. The only damage to buildings was the destruction of brick gables at Gas Station "B," First and Market Streets. Oakland cemeteries (R. Newcomb). — In the Mountain View Cemetery, which is on a little draw between ridges, the chief damage done was the cracking of the receiving vault, and that was not injured very much. In St. Mary's Cemetery, on the small ridge to the west, however, many monuments were moved or twisted and several were overthrown. On entering the cemetery from the east, very little damage was observed, but on climbing the ridge more and more was noticed. On the north slope less damage was done, and on level ground farther north ― 303 ―
absolutely no monuments were affected. Near the top of the ridge many monuments were overturned, and nearly all of them showed
twisting or shifting. The result of the shock upon the monuments in this cemetery may be summarily stated as follows:
Fifteen were rotated counter-clockwise, 4 of these thru from 1° to 2°; 6 thru 5°; 1 thru 15°; 3 thru from 5° to 8° with a lateral shift of 1 inch to the east; and 1 thru 8° with a lateral shift to the south. Six were rotated clockwise, 2 of them thru 25° to 30°; 1 thru 15°; 1 thru 10° with a lateral shift of 6 inches to the south; and 2 thru 2° with a shift to the south of 1 inch. Six fell to the east, 1 to the west, and 1 to the north. Three were shifted laterally from 0.5 to 1 inch to the east, one 1 inch to the southwest, and one 1 inch to the south. (B. McGregor.) — Of 12 monuments in Mountain View Cemetery that were disturbed by the earthquake, 10 are rectangular shafts which were simply twisted on their bases, 4 from left to right and 6 from right to left. The other 2 are turned shafts, both of which slid on their bases about 2 inches south. There were a few others displaced. Alameda. — The destruction was confined for the most part to the throw of chimneys and the upper portions of brick walls. A few tanks were also overthrown, and 3 large stacks near Pacific Avenue and Lina Street. Messrs. Pond and McFarland counted 619 fallen chimneys in the city; of these they report that 189 fell to the southwest, 143 to the southeast, 93 to the northwest, 97 to the northeast, 34 to the south, 14 to the north, 25 to the east, and 24 to the west. The fall of chimneys was evidently determined largely by the orientation of the houses, which have their walls in nearly all cases orientated at right angles to the direction given for the fall. The statistics are quoted not because they have any special significance, but because they indicate how little this class of phenomena contributes to the elucidation of the character of the earth movement, unless each particular case is studied in all its bearings. With regard to the chimneys which were dislocated and twisted, there appears to be more constancy of result. The same gentlemen counted 61 such chimneys and of these 58 were rotated counter-clockwise and 3 clockwise. Southeast of Oakland (G. Backus and R. P. O. Newcomb). — In the vicinity of High Street about half of the chimneys fell. The most general direction of the fall was to the north and south, altho some fell east and west when the slope of the roof was in that direction. Plastering in the houses was severely cracked, but no foundations nor buildings were damaged to any visible extent. A large smelter chimney in the vicinity was not damaged by the shock. At Fitchburg about the same state of damage was seen. The chimneys on the old houses were gone. A large school-house with a brick foundation was not injured. At Elmhurst the windows in the hotels and stores were broken. Most of the chimneys had fallen, one in particular being thrown to the east against the slope of the roof. At San Leandro half the windows in the stores were broken, and nearly every chimney was down. All loose objects in the houses, such as dishes, etc., were thrown down. The plastering was greatly cracked. The houses were not seriously damaged, and only 2 have been condemned. At Junction City the shock was about the same as at San Leandro. According to rumor a 3-inch fissure opened up between Junction and San Lorenzo, but this was not seen. The County Hospital, but a short distance from the Junction, was only slightly damaged. None of the chimneys were thrown over and plastering was not cracked. The Hospital is built on solid ground, and several quarries can be seen in the ground upon which the buildings are situated. ― 304 ―
At the San Lorenzo Cemetery, about half the tall monuments were down. Most of these fell to the south, some to the north, and a few to the east and west. Twisting occurs where the south end is thrown east. Almost all the chimneys in this vicinity were down. At Mills College about half the chimneys were down. A stone building there was badly shattered and will have to be taken down. A brick and concrete library, and the same kind of a bell-tower, were not injured to any great extent, tho a few cracks can be seen here and there. Mills is on rather high ground at the base of the foot-hills. (J. Keep.)—The floor of my room at Mills College seemed to be boiling. Immense damage was done. In the made ground there was a drop of from 1 foot to several feet. The seismograph registered for a time and then broke. The Science Hall, a stone structure, was badly injured, entailing a loss of $5,000. (J. N. Frank.)—In San Leandro objects against the east and west walls of the house were thrown down. Some statues were rotated clockwise. Chimneys were overthrown or broken, and plaster cracked, causing a damage estimated at between $400 and $500. Mount Eden (William Gall). — The general direction of the movement was to the north and northeast, but objects fell in all directions. Objects were rotated, some clockwise and some counter-clockwise. A rotary motion was distinctly felt. Brick chimneys were broken and thrown. Furniture was thrown flat. The shock caused consternation among the people and domestic animals. Monuments in the cemetery were overthrown in various directions. Decoto (F. E. Matthes). — No earth movements nor displacements were discovered anywhere along the base of the mountain scarp. The damage to buildings was slight, consisting of broken or twisted chimneys and cracking of plaster in a few houses. A few scattering chimneys escaped destruction, being probably better built than the average. In the stores and saloons articles were thrown down in southerly directions for the most part. Water was observed to splash from a tank a mile north of town, the direction of throw being southeasterly. The consensus of opinion was that the shock had a nearly north-south direction. According to the track-boss, the railroad track suffered no displacements anywhere between Niles and Irvington. The Masonic Home, a large brick structure located on the hillside on solid rock foundations, suffered but little damage. A few insignificant cracks in the brick walls, 2 chimneys broken off, and 2 chimneys cracked constitute the most serious damage. Plaster was cracked in several rooms; no windows were broken. Alvarado (F. E. Matthes). — The Alameda Sugar Company was the chief sufferer. The main buildings of the plant are of wood, substantially constructed, and were not damaged; but the fittings and accessory structures were injured in numerous places. An old lime-kiln showed diagonal cracks in the brickwork; several of the small arches above the fire holes opened and let bricks fall out. A 6-inch cast-iron water-pipe, attached vertically to the main building, broke transversely about 30 feet above the ground. The water in the tanks on the roof splashed so heavily as to raise and break the wooden covers. The water seems to have splashed mostly to the east. The 2 great platforms carrying the molasses tanks, supported by numerous vertical props 10 feet 10 inches high, resting on concrete foundations, fell down altogether; the northern one to the north, the southern one to the south, these directions probably being determined by the original inclination of the supports or the relative efficiency of the bracing. The tanks were all damaged and over 1,000,000 pounds of molasses flowed away. The total weight on the south platform was 1,072,891 pounds. (Plate 115A.) In the engine-room the vertical steam-pipes cracked next to the flanges by the wracking motion of the ceilings thru which they extended. The shock appears to have had a north-south direction, according to the position of the breaks in these pipes. ― 305 ―
The mill stands on flat, alluvial ground 100 feet north of Alameda Creek. Along the banks of the latter a large number of cracks extend, roughly parallel with the stream. Considerable masses next to the stream-bed slumped toward the same, leaving gaping cracks 1 to 2 feet wide, and carrying with them small outlying buildings, notably the fire-engine house, which moved bodily, concrete foundation and all, 2 feet south toward the creek. A small railroad trestle southwest of the mill moved 4 inches south on both of its abutments, probably owing to slumping of loose ground on the north side of the creek. A 2-inch water-pipe, laid under the ground some 60 feet north of the creek and almost parallel with the same, shows indications of having been submitted first to tension, causing rupture at one of the joints, then to sudden compression, causing it to be jammed together with violence. Cracks in the ground may be found as far as 250 feet from the creek. They were nearly all closed at the time of the visit (May 7), but were easily traced by the streaks of bluish-gray sand which has issued from them, together with considerable quantities of water. According to the Chinese cook of the superintendent, the cracks nearest to his dwelling opened and closed several times in succession during the quake; and large volumes of mud-laden water gushed from them, splashing up some 10 feet in the air at each closing. A large crack of this kind opened under the northwest corner of the dwelling, and the superintendent estimates that fully 500 gallons of water gushed from it, the flow continuing with decreasing volume for about an hour. The fence in front of the house shows that the ground there has been raised into a low hump. The sewer pipe leading west to the creek was detached from the house by a space of 22 inches. A chimney near the northeast corner of the house was thrown to the east with sufficient violence to throw the farthest bricks 35 feet east of the house. The top of the chimney was only 20 feet above the ground originally. In the roadway south of the mill, water oozed out in a number of places, without the production of visible cracks. The water pipes and hydrants in this vicinity were crusht in several places. At the Alvarado Water Works the brick buildings suffered considerable damage, the walls cracking in several places. Nothing could be learned regarding the behavior of the wells of this plant. The frame dwelling of the superintendent was damaged by the collapse of its underpinning. A similar fate befell the Alvarado Hotel. Both houses were being put in place at the date of the visit. At the school-house the water-tank fell owing to the collapse of its supports. Nearly all brick chimneys in the village fell, the directions varying. A few cracks opened across the streets, but these had been filled on the date of the visit. The consensus of opinion was that the shock had a north-south direction. Lick Observatory, Mount Hamilton. — From the reports of astronomers C. D. Perrine, R. G. Aitken, H. K. Palmer, K. Burns, A. M. Hobe, and G. A. Vogt the following observations as to the character and intensity of the shock have been obtained. The principal disturbance was preceded by a tremulous motion variously estimated at from 11 to 15 or 20 seconds. There seemed to be 2 maxima, the first being the stronger (?), according to H. K. P. There was a first secondary maximum about 5 seconds after the beginning, a maximum 11 seconds after the beginning, and another secondary maximum about 15 or 20 seconds after the beginning, according to K. B. A tremulous motion was felt after the principal disturbance. "Heavy vibrations were still felt 60 seconds after the first count. Motion was felt for nearly 2 minutes after the first count." C. D. P. "The duration of this tremulous motion was about 30 seconds. Vibrations stop in the house at the end of that time." K. B. "Duration between 30 and 35 seconds." A. M. H. No vertical motion was perceived, nor was any recorded on the Ewing seismograph. ― 306 ―
According to C. D. P., the heaviest movement seemed to be nearly east and west, while according to K. B. it was northwest and southeast. On the Ewing seismogram, the north and south component seems to be the most violent, the pen having left the plate for half a revolution of the plate. The east and west vibration was extremely large. The maximum of the east and west movement occurred after the pen of the north and south component left the plate. A razor strop hanging on a north wall, the only thing free to swing, swung east and west about a foot (double amplitude). A shaving brush which stood up on end and, being round, could fall in any direction, fell west. Things overturned fell east and west. The shock was severe enough to make windows rattle and doors swing. Book-cases were moved out about an inch from east and west walls, but not from north and south walls. A pendulum clock on a north wall stopt at 5h 12m 52s. Not much plaster fell, and only 1 of a dozen or more chimneys was thrown. Some other chimneys, principally those of a 3-story brick house, were cracked and shifted. The earth-waves were very long, but smooth. According to K. B., the shock was accompanied by a sound as of the flight of birds. The water in Smith Creek on the afternoon of the day of the shock was of a light slate color; not yellowish, as after heavy freshets. "Standing in the doorway and looking out the east window, I could see the walls of the brick house shaking. There seemed to be a great deal of dust in the air in front of the window." H. K. P. The movement of the east-west component of the Ewing seismograph indicates an intensity corresponding to an acceleration of 400 mm. per sec. per sec. The north and south pen left the plate, owing to the violence of the shock. Niles (R. Crandall). — The town of Niles stands on gravels of the alluvial fan at the mouth of the Niles Canyon, and is about 20 miles due east of the fault at its nearest point. At Niles there were no large buildings, and most of the structures were not strong, but there was no serious damage done to any of them. About 56 per cent of the houses had either terra-cotta chimneys or tin pipes, which are much harder to shake down than those of brick. Of all the chimneys in town, 48 per cent fell; of the brick chimneys 80 per cent fell; of the terra-cotta chimneys only 10 per cent went down. Most of the houses were not plastered, so no notes could be obtained on that subject. In nearly all of the houses such objects as dishes, bottles, vases, and clocks were thrown from the shelves. Milk and water were split from open receptacles in most cases. A concrete abutment of the bridge across Alameda Creek was cracked. A man out of doors at the time found much difficulty in walking. A 50,000-gallon water-tank fell at the Niles railway station. Similar tanks were thrown down at the stations at Pleasanton, Livermore, and Lathrop. This was due to imperfect construction rather than to the violence of the shock. The tanks were upon cast-iron pillars originally, but when new and larger locomotives were put into service on the railway, it was found necessary to have the water-tanks set higher. This was accomplished by inserting short blocks between the tanks and the tops of the pillars. When the weight of 200 tons was swayed on this sort of a structure, the tank collapsed. While at Niles, a visit was made to one of the new tunnels of the Western Pacific Railway, which is about 1 mile east of Niles in the Niles Canyon. The tunnel had penetrated about 130 feet into the hillside, but had not yet past thru anything but a sandy clay. During the previous winter the walls at the portal, and also on the inside, had stood without timbering. Since the earthquake it had been impossible to break out more than 4 feet of ground ahead of the timber sets without caving taking place. There had been an apparent movement in the soil which had removed its consistency and made it incoherent. The amount of water present in the tunnel was perceptibly changed. The foreman said ― 307 ―
that there was more water since the shock than there had been even in the wettest part of the winter.
Sunol (R. Crandall). — Sunol is a small town in the north end of Sunol Valley. The intensity of the earthquake there was of especial interest, because the town lies almost upon the line of the Sunol fault. This fault is the largest one known in the Mount Hamilton range, and has a northwest-southeast trend parallel to that of the San Andreas fault. It was expected that some compensating movement might be found to offset the slip along the San Andreas fault, and this Sunol fault was considered the one most likely to show that compensatory movement. The town stands partly on gravels and partly upon hard sandstone. The gravels are quite firm; much more so than the gravels on which the town of Niles is built. The gravels at Sunol are not thick, and the foundation is much firmer than that at Niles. It was quite apparent that Sunol had not felt the shock as severely as it had been felt at Niles, 6 miles to the west, or at Pleasanton, 6 miles farther east. Only a small percentage of the chimneys fell. Of other objects, few except bottles and vases fell; and a window was broken at the post-office. As there was no movement along the Sunol fault, the intensity at Sunol was less than at Niles, but the fact that it was also less than at Pleasanton shows that the difference must be in the formations underlying the two towns. (F. E. Matthes.) — Over 75 per cent of the chimneys in Sunol were broken. Some were twisted in a clockwise direction, while others were apparently thrown straight, most of them to the east. Many chimneys were cracked but were still in place. A few windows were broken, notably those of the post-office. The town is on alluvial ground, close to the hills. The depth of alluvium is estimated at the creek-bed to be about 50 feet. The steel bridge southeast of the town was found entirely undamaged. The flume between Sunol and Niles was damaged at a point 2.5 miles below Sunol. A few boards were knocked out of place, but the damage was slight and quickly repaired. The Apperson house, a substantially built structure with strong chimneys, had two of the chimneys twisted and one left intact. Verona (F. E. Matthes). — All the chimneys on the main house of the Hearst residence, 6 in number, were cracked, but none was thrown down. The studio has a long crack running immediately above the projecting beams supporting the roof, along the northeast wall, 18 inches from the eaves. No damage was occasioned to plaster or walls, except in the studio. The chimney of the power-plant, at the foot of the hill, was found cracked. The "cottage," built of wood, suffered no damage. No windows were broken. Pleasanton (R. Crandall). — The town is on a flat valley-floor composed of gravels, apparently the same as those at Sunol, but of a later age. Probably the Sunol gravels washt down from the hills to form a valley-floor. The ground upon which the town is built, then, is similar to that at Niles. The shock was felt quite sharply at Pleasanton, but not so much so as at Niles. Such articles as vases, clocks, and dishes fell in most cases and milk and water were spilt from open vessels. Practically no plaster fell, but houses that were plastered had numerous cracks in the walls. The intensity, as shown by falling chimneys, was as follows: 30 per cent of all chimneys fell; 48 per cent of the brick chimneys fell; 30 per cent of the chimneys were terra-cotta, but only 3 per cent of these fell; of the brick chimneys which did not fall, 30 per cent were cracked. (F. E. Matthes.) — About 50 per cent of all brick and tile chimneys in Pleasanton were thrown down. No marked preponderance in any one direction was noted. Nearly every brick building in town was somewhat injured. Cracks in the masonry and the dislodgment of occasional individual bricks in arches above windows and cornices constitute the principal damage. The only stone house, a 2-story saloon, suffered more severely than any of the brick buildings, the walls being badly cracked at the corners and even ― 308 ―
partly thrown down at the northwest corner. Wooden houses suffered no damage except the cracking of plaster. No window panes
were broken.
Two bridges near Pleasanton were inspected, one north of the town over Arroyo Valley and the other over Arroyo de la Laguna, 1.5 miles west of the town. These bridges rest on concrete abutments, and examination showed that in both cases the concrete had sheared horizontally by the longitudinal oscillations of the superstructure. The cracks were about even with the lower side of the stringers. In the case of the first bridge mentioned, these cracks extended to the wing wall at the south end. A vertical crack was also found near the west corner of the south abutment, running thru the entire height of the structure. A similar crack was also found at the east corner of the north abutment. The disposition of these vertical cracks seems to indicate torsional movements of the bridge, with right-handed rotation. The concrete was of poor quality, being traversed by streaks of coarse gravel alternating with others of finer texture. Thru the courtesy of F. H. Tibbets and Harold Woods, surveyors for the Pleasanton Hop Company, access was obtained to their records on well borings made in the neighborhood of Pleasanton. Most of these borings did not reach bedrock, but 2 of them did: one near the graveyard south of Pleasanton, which strikes disintegrated shales at a depth of 275 feet; the other 0.75 mile northeast of Pleasanton, just south of the railroad track, which strikes similar material at a depth of 180 feet. Livermore (F.E. Matthes). — Many chimneys were cracked and about 50 per cent thrown down. Several tall brick chimneys in various parts of the town were left intact. Those on brick piers between Livermore and Pleasanton were undamaged. A block of old, weak-looking buildings northeast of the depot suffered no more than a few cracks. Glassware in saloons and bars was thrown to the floor in quantities, in various directions. A heavy water-tank at the depot fell, owing to weakness of supports. The direction of the fall is north, but this is not necessarily indicative of the direction of the shock, as the wooden support probably gave way piecemeal. Concrete bridges about town were unhurt. The town is on alluvium. An interesting feature appears 0.25 mile north of Meyn's ranch, west of the road leading north from Livermore, about 2 miles north of that place. It is on the summit of a smoothly rounded hill, sloping gently down to an even, peaty meadow traversed by the arroyo of Cayetana Creek. The hill is really one of a number of spurs of the higher land south of the meadow. Its soil is peaty, with many sun cracks due to recent drying. Deep cattle tracks show that it must be quite soft in wet weather, much like the adjoining meadow. The summit of the hill in question was found crownded by a series of concentric deformations, rising stepwise above one another. A number of nearly concentric cracks were found extending northward into a sort of panhandle, along each of which an upward movement of the soil had apparently taken place. The uplift along the 2 principal cracks was found to be 19 and 16 inches, respectively. Along the minor cracks the vertical displacement amounted to an inch or two only. The surface of each step or bench was found to slope inward, and in some places the edge even appeared to have curled inward. The material must have been wet and more or less plastic at the time of the disturbance, but has since dried and hardened, as peaty soil will in dry weather. While the phenomenon is described by many as a "mud flow" or "mud spring," there are no indications whatever of a "flow," strictly speaking. The inward slope of the raised benches suggests the dropping back of the central portions after their upheaval; the scarps remaining, probably, owing to the friction between the opposite walls of the fissures, which prevented the complete return of the adjoining edges to their former level. The concen- tric arrangement of the cracks seems to indicate a centralized upward thrust, and the small diameter of the entire deformation shows that the effect of the thrust rapidly decreased away from the center. While there is no rock visible, it is quite possible ― 309 ―
that the hill has a sort of rock-core, some distance below the surface. The shock felt at Meyn's ranch was not particularly
violent and caused no damage to the buildings. (See plate 141A.)
(R. Crandall.) — Geologically, Livermore is on a floor similar to that of Pleasanton, but geographically it is about 6 miles farther east and farther from the San Andreas fault. The shock at Livermore was not severe, and but little real damage was done. A few objects of unstable nature fell, and in the larger number of cases milk and water were spilt from open vessels, but not in all cases. [1] Most of the houses in town were not plastered, but only a few of the plastered houses had the walls cracked, and in only one case was plaster known to have fallen. An excellent opportunity was afforded to see the effect of the motion upon pendulum clocks. In one jewelry store every such clock stopt, regardless of the direction in which the pendulum swung. One clock which had not been running before the earthquake, was started. Its pendulum swung in a northwest-southeast direction, as in the case of several clocks that stopt. About 5 per cent of the brick chimneys fell, with less than 15 per cent cracked. A curious phenomenon was observed near Livermore, the explanation of which is not clear. At the Alviso ranch, a little over a mile north of the town, the top of a small hill was broken up at the time of the earthquake. The breaking of the ground did not consist of fissuring along a line, but was in the nature of an uplift of a limited area. There were 3 fairly well marked concentric rings where the ground had broken, the inside ring in each case being forced higher than the outside ring. The effect was similar to that obtained by placing 3 plates of different sizes within each other. The accompanying photograph (plate 141A) shows this feature fairly well. It was said by people in the vicinity that there was mud in the cracks at the time of the earthquake, but there were no evidences of any at the time of the writer's visit several weeks after the shock. [2] (Elmer G. Still.) — The Southern Pacific Company's 20,000-gallon water-tank fell in a north-northwest direction; tombstones fell in various directions; a hanging lamp was caused to swing counter-clockwise, with the longer diameter of its orbit east and west. Mr. Still was asleep and was awakened by the bed being shaken north and south; the motion after that was in every direction. Water spilt from full tanks mostly on the east and west sides. Mr. Still reports that where the ground was deformed in concentric ridges, as described by Mr. Matthes and Mr. Crandall, there was an alkaline spring years ago. Santa Rita, 3 miles east of Dublin (F. E. Matthes). — A small, flat levee along the east bank of Tassajara Creek, immediately north of the main road, showed several somewhat crescentic cracks along which the ground had slipt down and toward the creek from 1 to 3 inches. These cracks extended farther south, according to local settlers, and crost the road; but this was no longer traceable at the time of the visit. Chimneys had fallen on all the houses, but as they were not of brick the damage was slight. In the grocery store and bar-room articles were thrown in a southerly direction. Dublin (F. E. Matthes). — The damage consisted of a few chimneys broken off, and articles thrown down from shelves and counters. A water-tank 2 miles east fell from its supports, probably owing to the weakness of the latter. Several other tanks in the neighborhood were injured. San Ramon (F. E. Matthes). — Most chimneys had fallen. San Ramon saloon, south of the bridge, slid off its foundations in a northerly direction. The west end moved 3 feet, the east end about 15 inches, being stopt by a fence-post. Several window panes ― 310 ―
were broken in the building, and glassware was wrecked in quantities. Neither church nor school-house suffered any damage.
The shock was mostly in a north-south direction.
Danville (F. E. Matthes). — Most chimneys were cracked or twisted; a few were broken off completely. Glassware in saloons and goods in a grocery store were thrown down in quantities in various directions. Water was observed to splash out from two tanks in the village, in a southerly direction in each case. Water-pipes laid over the surface of the ground at a neighboring ranch were reported to have been thrown out of alinement. Walnut Creek (F. E. Matthes). — About 50 per cent of all chimneys were thrown down. A water-tank at the livery stable fell. Goods in the grocery store were thrown down in quantities. The direction of the shock was not ascertainable. Two barns, weak structures, were moved slightly from their foundations. Plaster in several houses was cracked. Clayton (G. D. Louderback). — At the northern base of Mount Diablo the intensity of the shock was much less than in the alluviated valley-bottom at Concord. No chimneys were thrown down, and no dishes nor glassware were knocked off shelves, but milk in pans was skimmed by the rocking motion. On a hillside above Peach Tree Spring, on the west side of Mount Diablo and very near the contact of the Knoxville shales and the Franciscan, a crack opened in the ground about 30 feet long, in a north and south direction, gaping 4.5 inches. Concord (F. E. Matthes). — Conditions here were much the same as at Walnut Creek. The only brick building, a bank, was cracked. Most of the chimneys were cracked, and about 50 per cent had fallen. A water-tank at the depot was thrown down. Martinez (F. E. Matthes). — Most of the brick buildings here suffered severely; nearly all are more or less cracked, and the stone facing of several was partly demolished. The roofs of the bank and other buildings were wrecked. A small stone house, built of large blocks, was completely ruined, probably owing to vigorous vibrations of an adjoining wooden water-tower near the Alhambra Hotel. The stones started in the east abutment of Main Street bridge. Many window-panes were broken. Most of the chimneys were broken off. The court-house was little injured, except for the pediment above the entrance, where many large stones have been loosened. One of the chimneys of the Bull's Head Oil Works lost a corner; the others were left undamaged. The railroad track east of Martinez, near Bull's Head Oil Works, was thrown 3 inches out of alinement to the north. Many cracks occurred in the embankment on both sides of the track. A series of 5 small transverse waves was found in the embankment about 0.5 mile west of Peyton Station. The distance between crests was about 10 to 15 feet; amplitude estimated at 3 inches. This embankment lies in flat marshy land. A small railroad bridge near Avon Station was thrown 4 inches toward the east abutment, but it had been repaired at the time of the visit. (W. Stoddard.) — Buildings were loosened in general, the fronts of some falling out. The north and south walls seemed to suffer most. Parts of a large wooden building, particularly the window-sashes, were moved in a southwesterly direction. The wooden props supporting another building were tilted a little toward the southwest. Another building was moved 0.5 inch toward the south. The southern part of the town was damaged more than the northern part. In the cemetery 6 slabs and pillars fell a little east of north; 2 pillars fell to the west; 2 pillars were twisted on their bases and shifted to the west; 1 pillar was tilted to the south immediately next one which fell to the east. A clock at the court-house had its pendulum broken. The pendulum was about 2 feet long. The level of the underground water rose after the shock. Cornwall and Black Diamond (E. S. Larsen). — The towns are about 0.5 mile apart, both located on the bay flat and underlain by a tough hardpan. A very few things ― 311 ―
were thrown from shelves; one rickety chimney was thrown, and one concrete wall in process of construction fell. Less than
half the clocks were stopt, though nearly all sleepers were awakened. Most of the houses are small and have terra-cotta chimneys.
Antioch (E. S. Larsen). — Antioch is on the same sort of ground as Cornwall, but there are more brick buildings and more moderate-sized buildings with brick chimneys. A few chimneys were twisted on their bases, several were thrown entirely and about 25 per cent of them needed repairing after the shock. Out of about 12 brick buildings, the tower of the Catholic church was somewhat damaged, and one rickety old brick building fell. None of the good buildings were damaged. A couple of windows were broken, a few clocks were stopt, and a few things were thrown from shelves. Top-heavy statuettes tipt over. All sleepers were awakened. Things generally moved north and south, or northwest and southeast, which seemed to be the general impression of the direction. Bethany, San Joaquin County (Mr. Schichtman). — The movement was from northeast to southwest, and was sufficient to splash water from a full trough, but not strong enough to overthrow objects. Byron Hot Springs, Contra Costa County. — The springs, some 30 in number, hot and cold, were not affected by the earthquake. One chimney and some plaster were cracked and a picture was thrown from the wall. The shock was considered quite severe, though the damage was slight. Tracy (R. Crandall). — Tracy, in the San Joaquin Valley, lies at the foot of the range separating Livermore Valley from San Joaquin Valley. The shock was not at all severe; in fact it was spoken of by several as being no heavier than the jarring often occasioned by heavy engines starting a loaded train. Very few objects fell, and in only one case was any damage done to a building. This was the cracking of a 2-story brick building which did not appear to be especially well constructed. Only one brick chimney cracked, and none fell; so it would appear that the building cracked because of the poor construction rather than because of the intensity of the earthquake. Milk or water was spilt in only few cases — not over 30 per cent. The water-tank of the Southern Pacific railroad at Tracy fell, as did similar tanks at Livermore, Pleasanton, and Lathrop. The reason for this is explained in the description on a preceding page of the construction of the tank supports at Niles. Lathrop (R. Crandall). — This is a small town upon the floor of the San Joaquin Valley, about 12 miles east of Tracy. The intensity was about the same as at Tracy. There was no appreciable difference in the number of fallen objects or stopt clocks, the main difference being that a considerable number of people were not alarmed enough to get up. One man who was up experienced no difficulty in standing or walking. The general impression is that the shock was slightly lighter than at Tracy, Stockton (R. Crandall). — Stockton is about 10 miles north of Lathrop, but not much farther east. As it is a much larger place, it was easier to see the effects of the earthquake. Not as much detailed work was done in Stockton as at the other places, since it was known that Mr. Edward Hughes was collecting data in that city. The shock was felt with alarm by people in houses and on the ground. The motion was spoken of as being a rolling motion like that felt on board ship. Almost no objects fell, even in houses where there were tall vases and similar bric-à-brac. At one drug store two little vials fell from the shelves; at another even built-up pyramids of various articles for window display were undisturbed. Milk and water were spilt in a very few cases. Splashing of milk up the sides of the pans was noted by a few persons, and the direction was given as northwest and southeast. Many clocks were stopt, but there was nothing consistent in the direction of pendulum motion. All of the big brick buildings were visited, and no damage was found except in an old 2-story building which seemed merely to have ― 312 ―
had an old crack widened, due to the settling of the foundation. The City Hall had considerable plaster cracked, but this
was due to the swaying of a 50,000-gallon tank on the roof. Three chimneys were cracked, and one was reported to have fallen,
but this was not verified. At the houses where the chimneys were cracked, milk was not spilt from open pans, so it is apparent
that the chimneys were faulty and not that the earthquake was severe.
(E. Hughes.) — A careful and exhaustive inquiry was made at Stockton by Mr. Edward Hughes, under the direction of Prof. J. C. Branner, and the following notes are contributed by him: The shock, while strong enough to alarm many of our people, was chiefly notable for the absence of the destructive effects experienced in many less fortunate localities. It began with a gentle trembling motion, which increased slowly for the first 5 or 6 seconds, then rapidly to a maximum of rough jolting shocks lasting perhaps 5 seconds. These were followed by a series of long, smooth vibrations, which gradually decreased in amplitude until no longer perceptible. The effects, as noted by many observers, would indicate that the heavier shocks traveled in a northwest-southeast direction, while the smooth oscillations which marked the latter part of the disturbance ran nearly eastwest. The immediate effects, as noted in dwellings, during the shock were the creaking and straining of buildings, the swinging of doors, the rattling of window weights and pictures on the walls, the swinging of chandeliers and drop-lights, and the stopping of clocks. Out of doors, some observers claim to have noticed the swaying of tall buildings and smoke-stacks; and many mention the violent motion of the trees, the branches of which lasht together as if in a storm. Birds frightened from their resting places flew in confusion, and the air was filled with their startled cries. A careful canvass of the city gives the following results in the way of damages sustained: There were a few small cracks in the arches in the hallways of the county court-house. It is safe to attribute this to faulty construction rather than to the violence of the shock, as a number of large cracks had opened in various parts of the building soon after it was finished. One water-tank was overturned, the supporting framework being insufficiently braced; this tank fell about 15° east of south. A large gasometer at the natural gas well on north Commerce Street was slightly damaged. Castings supporting the guide wheels were broken, and the gas tank was slightly twisted to the left so that the guide wheels were thrown off the guides. In two or three cases in the city, the tops of chimneys fell off. Examination showed that the mortar had never properly united with the bricks, owing probably to their dryness when laid. In several cases houses suffered damage by the spilling of water from attic tanks. Aside from these cases of relatively insignificant damage, everything gives testimony to the comparative gentleness of the shock. In china stores, where fragile wares were displayed in all sorts of insecure positions, not a piece was displaced or broken. So far as can be learned, no plaster fell anywhere in the city, and there was no breakage of bric-&-grave;brac or china in the dwellings. Observers who watched the minute hands of clocks that were not stopt estimate the duration of the shock at from 30 to 40 seconds. The heavier shocks were undoubtedly from northwest to southeast. This was shown in several ways. Tanks spilt water in both these directions, and the tank noted above fell nearly to the southeast, although its frame ran approximately east and west, and so offered some resistance to free motion to the southeast. In McCloud's Lake, the waves ran northwest-southeast, breaking highest on the bank and bulkhead in the southeast corner, while the north side was little affected. At the city pumping station on Mormon Channel, a similar effect was noted. Several observers claim to have seen tall buildings and stacks swaying in the direction indicated, and those who were standing were conscious ― 313 ―
of the movement of their own bodies in the same direction. Milk in open vessels left a coating of cream highest on the northwest
and southeast sides, although in many cases motion was also shown east and west.
While there is not entire agreement with reference to the east and west vibrations during the latter part of the shock, the larger number of observers plainly felt and saw their effects, and the evidence as to their occurrence seems conclusive. Doors swung east and west; swinging objects, such as drop-lights, hanging baskets, etc., were found either swinging east and west or in circles after the shock, and pictures hung on north and south walls of rooms showed lateral motion during the latter part of it. Tanks in several cases split water east and west, although not in such quantities as in the other directions. The following table indicates the effect of the shock on the 128 clocks concerning which reports were received:
Clocks with very long or very short pendulums were generally not stopt. Two town clocks were not stopt. One of these, which, through the courtesy of Mr. E. B. Condy, I was permitted to examine, is in the tower of the county court-house. Its frame stands northeast and southwest; and its 100-pound pendulum, hung on the northwest side of the frame, swings northeast and southwest, missing the edge of the iron stand about 0.5 inch. A deep scar in the mahogany pendulum bar indicates that during the shock the pendulum swung sharply to the southeast, its bar striking the edge of the iron stand. The weights of the same clock hang in a narrow shaft at the side of the tower. The wire pulley cords which support the weights were found so badly twisted as to interfere with winding the clock a day or two after the earthquake. On the inside of many clock-cases are found scars made by the striking of the pendulums. These scars are deepest on the south side in clocks facing east or west, and on the west side in clocks facing north or south. Some persons who were outdoors during the shock claim to have heard a dull rumbling sound immediately preceding it. They find it difficult to describe the sound accurately, and in some cases think it may have emanated from nearby buildings. A considerable number of people suffered from nausea and dizziness, with headache, for a time after the shock. With some these disagreeable symptoms persisted all the following day. Farmington, San Joaquin County (J. F. Gwin). — The house quivered, then the sash weights of the windows began striking back and forth, and a heavy rolling motion was felt which caused open doors to swing back and forth. The clock stopt. The surface of the ground moved in waves like water, and trees moved with the ground. Central San Joaquin County (E. P. Higby). — In Ranges 6 and 7 E., townships 1 and 2 N., Mount Diablo Meridian and Base line, there were apparently 2 maxima of equal intensity with intervals of a few seconds between. The apparent direction was SW. to NE. No objects nor chimneys were overthrown. The bed shook, and chandeliers, pictures, open doors and shutters were caused to swing. Windows and window weights rattled. The clock did not stop. Paper on the walls was cracked. The slate roof on a high church tower was cracked. There was scarcely a breath of wind, yet large trees swayed and bent as if rocked by a terrible gale. Water in the wind-mill tank and in other tanks slopt ― 314 ―
over, and continued to do so for 5 minutes after the shock. Water was thrown from a swimming tank where the level was 5 feet
below the top of the tank; water at one place in the river was thrown over a concrete wall 8 or 9 feet high.
Modesto (E. Hughes). — In common with other points in the great interior valley region, Modesto received a very decided shaking up by the earthquake, but suffered practically no damage. The local effects were the stopping of clocks, the swaying of trees, hanging baskets, drop-lights, and chandeliers; and in a few cases the fall of objects from insecure positions in stores and dwellings. Water tanks and troughs, milk pans, etc., spilt part of their contents, and in one or two instances cracks opened in buildings. No one, so far as known, actually timed the duration of the shock in seconds. The observations of many persons in and near the town indicate that the vibrations were in two principal directions: viz., northwest-southeast and approximately west-east. The heavier shock seems to have been in the first direction, but observers are not in entire agreement on this point. Clocks of larger size were quite generally stopt, no matter in what direction they faced. Several persons report having heard a roaring or rumbling sound, beginning a few seconds before and continuing until the end of the disturbance; and a number of people were affected by symptoms somewhat like seasickness for several hours after it. The following detailed notes were obtained from citizens of Modesto and vicinity: (Mr. Schaffer.)—Trees swayed northwest-southeast. "The Swan," a new building with green walls, cracked at the junction of the ceiling with the northeast end wall; also at the junction of the ceiling with the fire-wall running thru the center of the building from northwest to southeast. The cracks in both cases were on the second (the top) floor. The building faces northwest. (Player's Drug Store.)—Boxes on shelves on the northwest side of the store fell toward the southeast. (Mr. Swanson.)—Saw water spilt southeast-northwest from the railway tank at the depot. (Al Fogarty.)—Meat market. Mr. Fogarty ran from the building, and on returning after the shock he found drop-lights and a butchers' scale, suspended by a single wire from the ceiling, swinging in a direction parallel with the street, northwest-southeast. (Green Brothers.)—Heard a roaring sound just before the shock. Felt the bed swing northwest-southeast. Plaster sifted down from cracks in the ceiling. (E. E. Woods.)—Mirror hanging from southeast wall fell, on account of breaking of the cord, on its face toward the northwest. (Mr. Chapman.)—Ranch 5 miles southwest of Modesto. Water trough oriented north-south spilt water from both ends. (George T. McCabe.)—The bed was standing north-south. The first motion was east-west, the second and maximum motion was northwest-southeast. Trees swayed northwest-southeast. The window sash dropt. (Mr. Rider.)—Water in the street gutters moved west-east in the first part of the shock; in the second part, northwest-southeast. (Mr. Schaffer.)—Twenty-one miles southeast of Modesto. The sliding doors on a barn fronting east moved north and south repeatedly during the shock. A water trough a few feet away spilt water east and west. (Johnson and Ross Store.)—A pile of paint cans stood northwest-southeast. Several cans fell to the northeast. (G. W. Elsey.)—A tall, open-framed "Mission" clock facing southeast was found after the shock with its pendulum lodged on the top of a cross-bar of the frame. The position of the pendulum indicated a considerable increase in the amplitude of its vibration northeast-southwest in order to allow it to swing high enough to lodge. There were several ― 315 ―
similar cases of lodged pendulums in clocks facing in the same direction. Mr. E. Elsey also noted a water-tank spilt east
and west, and trees swayed in the same direction. He heard a rumbling sound.
(H. Hintze.) — A water-tank spilt east and west. A hanging lamp swung in the same direction, dropping its chimney to the east. A bed on the porch rolled east and west. He heard a rumbling sound during the shock. (Editor of the Daily Herald.) — Bed moved northwest-southeast. (Farmers' and Merchants' Bank.) — The vault is built upon a foundation independent of the rest of the building. The front of the vault, facing southwest, is continuous with a lath and plaster partition which extends to the ceiling. On the left is a wash-room, and on the right an opening into the room at the side and back of the vault. The plaster partition is cracked where it joins the top of the vault and part way down the sides, probably indicating a greater amplitude of motion in the building than in the more solidly constructed vault. (W. A. Harter.) — At Ceres, 6 miles south of Modesto, a tank spilt north-south. (W. R. High.) — One mile north of Modesto, a tank spilt north and south during the early part of the shock, and east and west later. Trees swayed north-south. (Empire Stables.) — Drop-lights swung and water in trough spilt northwest-southeast. (A. L. Holtham.) — Milk pans on shelf supported by wires spilt milk west. The shock was preceded by a roaring sound. (Modesto Gas Works.) — Water in the gasometer tanks spilt northwest-southeast. A chandelier in the building hung by a 0.375 inch gas-pipe 12 feet long; after the shock was over this chandelier was swinging northeast-southwest. (J. T. McNeely.) — Station agent saw the railroad water-tank spill northwest-southeast. (Editor of the News). — A water-tank belonging to J. Urie, 2.5 miles southwest of Modesto, was overthrown to the west. The following were the clock records at Modesto:
Ceres, Stanislaus County. — The shock was felt, but is reported as not severe. Oakdale, Stanislaus County (F. G. Keid). — The shock seemed to be in a northeast and southwest direction. In the school-house, a 2-story brick building, timbers lying in a northeast and southwest direction were loosened from the concrete at the ends, but those extending normal to this were not affected. Clocks stopt. (E. C. Crawford.) — A flag-pole 110 feet high swayed apparently north and south; 2 clocks stopt; water in a tub moved north and south; and a stand lamp seemed to tip slightly north and south until steadied; but no objects were overturned. Westley, Stanislaus County (W. G. Carey). — The town is on adobe soil with gravel at a depth of 20 feet. Furniture and pianos were moved across floors from the walls toward the south, and quite a number of pieces of furniture were toppled over. No chimneys were damaged, but several large water-tanks were demolished. These demolished watertanks thru the country seem to have been rotated about one-fifth counter-clockwise. Cars on the track were moved at least a foot. At the railway depot, a 1,400-pound iron wheel was rolled back and forth for a distance of 9 feet northwest and southeast. There ― 316 ―
were 2 maxima in the movement of the earth, and the second was the stronger. Some men sleeping on a scow on the river 2 miles
east of Westley heard a rumbling sound before any shock was felt, and came out of the scow to see what it was. Then the shock
came and the waters rolled and foamed.
Coast Ranges East of the Rift and South of Mount Hamilton, and the
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| Water: Sand = 20:80 | Water: Sand = 17:83 | Water: Sand = 15:85 | ||||||
| Frequency | Amplitude in Centimeters | Frequency | Amplitude in Centimeters | Frequency | Amplitude in Centimeters | |||
| Car | Block | Car | Block | Car | Block | |||
| .5 | 6.1 | 9.5 | .6 | 6.0 | 7.9 | .9 | 6.1 | 6.3 |
| .75 | 6.1 | 9.7 | 1.0 | 6.0 | 8.5 | 1.7 | 6.2 | 7.4 |
| 1.0 | 6.1 | 9.5 | 1.4 | 6.0 | 9.0 | 2.6 | 6.4 | 8.1 |
| 1.3 | 6.1 | 9.2 | 1.6 | 6.1 | 9.3 | 3.3 | 6.5 | 8.4 |
| 1.5 | 6.1 | 7.3 | 2.3 | 6.1 | 9.5 | 3.6 | 6.3 | 8.0 |
| 2.0 | 6.2 | 5.9 | 2.4 | 6.1 | 7.5 | —— | —— | —— |
| 3.2 | 6.3 | 1.9 | 2.8 | 6.1 | 8.0 | 1.0 | 3.2 | 3.4 |
| 3.5 | 6.4 | .3 | 3.6 | 6.4 | 4.4 | 1.2 | 3.3 | 3.8 |
| —— | —— | —— | 3.8 | 6.4 | 4.3 | 1.8 | 3.3 | 4.4 |
| .83 | 4.3 | 7.4 | —— | —— | —— | 2.7 | 3.4 | 4.7 |
| 1.0 | 4.3 | 7.2 | .85 | 3.3 | 5.2 | 3.2 | 3.4 | 5.1 |
| 1.3 | 4.3 | 6.5 | 1.5 | 3.3 | 5.3 | 3.9 | 3.4 | 5.2 |
| 2.1 | 4.3 | 3.5 | 2.5 | 3.3 | 5.4 | 4.0 | 3.4 | 5.0 |
| 3.0 | 4.3 | 2.4 | 3.1 | 3.4 | 4.3 | 4.6 | 3.6 | 5.5 |
| 4.0 | 4.5 | 1.2 | 4.1 | 3.5 | 2.2 | |||
| Water: Sand = 12:88. | Water: Sand = 10:90 WATER: Sand = 20:80 Two layers | Dry Gravel. | Wet Gravel. | ||||||||
| Frequency | Amplitude in Centimeters | Frequency | Amplitude in Centimeters | Frequency | Amplitude in Centimeters | Frequency | Amplitude in Centimeters | ||||
| Car | Block | Car | Block | Car | Block | Car | Block | ||||
| 1.8 | 6.2 | 6.3 | 1.4 | 4.4 | 4.5 | 2.5 | 4.6 | 4.6 | 1.9 | 4.6 | 4.6 |
| 2.5 | 6.4 | 6.4 | 2.0 | 4.7 | 6.3 | 2.8 | 4.6 | 4.9 | 2.7 | 4.8 | 4.9 |
| 2.8 | 6.2 | 6.4 | 2.3 | 4.7 | 6.4 | 3.2 | 4.7 | 5.2 | 3.2 | 4.8 | 5.3 |
| 3.2 | 6.7 | 7.0 | 2.5 | 4.7 | 6.5 | 3.3 | 4.8 | 5.4 | 3.4 | 4.7 | 5.8 |
| —— | —— | —— | 2.6 | 4.6 | 6.0 | 3.5 | 4.8 | 5.4 | 3.3 | 4.7 | 5.9 |
| 1.0 | 3.1 | 3.1 | 2.6 | 4.8 | 5.5 | 3.7 | 4.8 | 5.0 | 3.4 | 4.5 | 5.7 |
| 1.8 | 3.2 | 3.2 | 3.2 | 4.7 | 3.8 | 3.8 | 4.9 | 5.2 | 3.4 | 4.7 | 5.8 |
| 3.3 | 3.3 | 3.4 | 3.4 | 3.8 | 3.9 | 4.8 | 5.3 | ||||
| 3.8 | 3.4 | 3.7 | —— | —— | —— | —— | —— | —— | |||
| 4.0 | 3.4 | 3.8 | |||||||||
| 4.2 | 3.5 | 3.8 | |||||||||
In the above discussion we have been solely concerned with the motion of the block embedded in the sand in the middle of the car. The sand on the bottom and near the ends of the car has but little relative motion with respect to the car. A board thrust downward into the sand showed by its motion that the relative motion of the sand with
It doubtless frequently happens in river valleys, coastal plains, or "made land" that a very soft water-soaked subsoil is covered with a crust of more solid ground. This condition of affairs was imitated on a small scale. A lower layer 13 cm. thick of very wet sand containing 20 per cent of water was covered by a piece of oilcloth, and upon this was placed a layer 12 cm. thick of much drier sand containing 10 per cent of water, and tamped into as compact a condition as possible. The block carrying the tracing pencil was embedded in this upper layer. If the whole load of sand had been like the top layer, it would have oscillated almost perfectly with the car. No such result was obtained with the two layers. When the car was shaken, it was apparent that there was still considerable freedom of motion in the lower layer. The upper layer moved as though it were floating on a semi-fluid mass. It rose and fell at the ends, and this motion extended to the middle, causing the block to rock back and forth, a result which was not obtained when the car contained a load of uniform consistency. The to-and-fro motion of the block was considerably greater than that of the car, for frequencies of 2 or 3 per second. For frequencies greater than 3, the amplitude of the block was less than that of the car. The results of this experiment are given in the tables on p. 330, while a plot of the same is included in fig. 62. The results, however, do not do justice to the possible destructiveness of such a motion. The rocking motion of the upper layer, as well as the violent manner in which it was broken up into fissures and ridges, seems to show that the destructive effect of the shaking motion of a semi-fluid mass may be increased when it is confined by a superincumbent layer of much more solid and compact material.
In the last experiment with the shaking machine, the car was loaded with coarse gravel. The gravel consisted of water-worn pebbles of all sizes up to 2 inches in diameter. It contained no clay nor sand to bind the gravel together. When this load of dry gravel was shaken, the block embedded in the gravel moved with the same amplitude as the car until the frequency reached 3 double vibrations per second. With higher frequencies the amplitude of the block was somewhat greater. Considerable water was then poured into the car, and it was again shaken with various frequencies. The results were similar to those obtained with the dry gravel, except that the relative motion of the gravel with respect to the car was nearly twice as great as in the case of the dry gravel. The data for these experiments are given in the table, while a plot of the same is given in fig. 62.
A consideration of the meager and more or less erratic data described above suggests various questions and criticisms. It has already been explained why more extensive experiments involving other materrials were not undertaken. The erratic nature of the experimental data is not due to the method of experimentation employed, but to the uncertain and varying condition of the material with which the car was loaded. If, in the beginning of a series of experiments, the composition of the load was thoroly uniform, this was no proof that it remained so. A few moments of shaking sufficed to change to a greater or less extent this uniformity. When the material contained a large percentage of water, continued shaking caused the material close up to the ends of the car to pack and become somewhat drier; this was also true, tho to a much less extent, of the middle portion. The portion midway between the ends and the middle, where the relative motion of contiguous portions of the load was the greatest (thus causing fissures and ridges to develop), noticeably increased its content of water. This development of non-uniformity in the consistency and composition of the load is a sufficient explanation of the irregularity of the results obtained.
With regard to the scale on which the experiment was performed, the question naturally occurs: Would similar results have been obtained if the car were very much larger? One can not be certain, but it seems that such would have been the case if the frequency and amplitude of the car's motion were the same. Several experiments were performed with a depth of 15 cm. and 25 cm., and the results were substantially the same. The car was also divided by partitions running at right angles to the direction of motion, making a compartment of only half the length. The results tabulated below show that, at least in this case, the motion of the block embedded in the sand was not greatly affected by the presence of the partitions.
| Length of car between partitions in cm. | 101 | 49 | 101 | 101 | 49 | 49 | 101 |
| Frequency in double vibrations per sec. | 2.2 | 2.25 | 2.3 | 2.1 | 2.4 | 2.15 | 2.25 |
| Amplitude of car in cm. | 7.5 | 7.6 | 7.7 | 7.6 | 7.5 | 7.5 | 7.5 |
| Amplitude of block in sand in cm. | 11.9 | 9.3 | 11.3 | 10.8 | 10.8 | 11.4 | 11.8 |
In the experiment just described the material used contained 20 per cent water; with less water the partitions would doubtless have a greater effect in restricting the motion. It is also probable that with a larger car the relative motion of car and load would have been greater.
Another question which is likely to occur is: Does the solid or semi-fluid mass with which the car is loaded have a free period of its own which is comparable with the vibrations imprest upon it by the to-and-fro motion of the car? To elucidate this matter, the car was partially filled with water and the free period of gravitational waves determined experimentally. The frequency of such waves was found to be 1.06. However, the load, instead of being like water, was in all cases exceedingly viscous and plastic. This condition would in any case decrease the natural vibration frequency of the load, and in the present case the viscosity was so great that the load could not possibly have any vibration independently of the oscillatory motion of the car.
Finally the question may be asked: What is the explanation of the fact that the load on the car (or the major part of it) oscillates thru a greater amplitude than the car which causes the motion? At present I have no comprehensive explanation of this fact. It undoubtedly depends upon the inertia of the load, combined with the greater or less freedom with which it yields to imprest forces. The load in the car is set into motion by two sets of forces: (1) On account of the motion of the bottom of the car a tangential force is exerted on the bottom of the load and this is transmitted upwards by the rigidity of the load, or, exprest otherwise, by the mutual friction of successive layers of the load. (2) On account of the advancing motion of the end of the car the load receives a thrust which is transmitted thru the material by its resistance to compression. Sometimes one of these sets of forces is of greater importance, and sometimes the other. One would be apt to think the end thrust was of the greater importance, but this is certainly not always the case, for when the load consists of a mound not resting against either end of the car, the block embedded in the top of the mound may oscillate with a much greater amplitude than the car. (This was experimentally demonstrated.) In this case there can be no end thrust whatever. In some cases the end thrust may be more effective than the tangential force; this is probably the case when the frequency of motion is rather high.
To those interested in seismology the important question is: How do these experiments help to explain the greater destructiveness of earthquakes in regions where foundations are in alluvial soil than where foundations rest directly upon rocky strata? To pass from experiments upon a box containing half a ton of soil to the destructive effects of an earthquake is certainly a great leap. In taking such a step, one is very likely to make mistakes. However, it seems to me beyond question that a soft, semi-fluid mass of
In the preceding pages, all the data significant of the distribution of the intensity of the shock of April 18, 1906, have been set forth in such detail as seemed to be warranted in a statement of fact. The general conclusions drawn from the data are represented graphically upon the intensity map No. 23. It is proposed here, however, to call attention to some of the more interesting and instructive phases of the distribution of intensity, and briefly to discuss their significance.
It is to be noted, in the first place, that the region over which the disturbance was felt, extending from the Pacific Coast to Central Nevada, and from southern Oregon to southern California, is one of varied physiography. In a consideration of the relation of the physiographic features to the distribution of intensity, it will be necessary to distinguish only two classes of features; viz., (1) the mountain and hill slopes, generally underlain by firm rocks and veneered for the most part with a thin mantle of regolith and soil; and (2) the valley-bottoms usually underlain by a relatively great depth of infilled alluvium in a little coherent condition, and for the most part saturated with ground-water.
The color bands on the map, indicating the gradation of intensity, show very considerable irregularities, or departures from the smooth curves which might reasonably be expected to obtain as the expression of such gradation of absorption of energy in homogeneous materials. To some extent such irregularities may be ascribed to the known lack of homogeneity in the firm elastic rocks of which the earth's crust is chiefly composed. But the irregularities referred to are too great to permit us to regard such lack of homogeneity in the underlying elastic rocks as an important factor in determining them. The irregularities are clearly related to the distribution of the valley lands.
If now, before entering upon a consideration of these irregularities, we endeavor to ignore them, and so obtain a general conspectus of the color bands representing the gradation of intensity, the following features come out fairly clearly:
1. On the northeast side of the fault-trace, the zones of equal gradation of intensity show a tendency to belly out to the northeastward, opposite the middle portion of the fault-trace. This tendency is most pronounced in the grades from VII to II of the Rossi-Forel scale, and is apparent in all grades below IX.
The irregularities above referred to, associated with the distribution of valley lands, confuse somewhat the perception of this tendency, but do not detract from its reality.
2. As a partial statement of the same general fact, the color zones become distinctly narrower, and their boundaries converge, as they approach the coast north of Eureka. This feature of the distribution of intensity clearly suggests that the isoseismal curves close in and swing around the end of the fault, and that there is, therefore, no indication of a submarine prolongation of the fault beyond its known extent on the mainland in Humboldt County.
3. The zones of equal gradation from IX to V of the scale are narrower at the southern end of the fault-trace than at the northern end, and they close around the end much more closely. This fact is suggestive of less depth of disturbance at the southern end of the fault. But the general disposition in the south of the zones ranging from V to II is not essentially dissimilar to those in the north.
4. The disposition of the isoseismal curves along the coastal territory between Point Arena and Shelter Cove indicates that the trace of the fault on the sea-floor lies but a few miles off shore, and that its course partakes of the nature of a very obtuse sigmoid curve, approximately parallel to the trend of the coast. It follows from this inference that the fault observed in Humboldt County is continuous with that extending from the vicinity of Point Arena southeastward. No facts have come to light which weaken this conclusion, altho all the facts have been diligently sought for.
5. On the southwest side of the fault, the territory upon which it has been possible to trace the isoseismals, particularly those ranging above VI, is very much smaller than on the northeast side. In so far as the territory available is representative of the entire southwestern crustal block, it appears, chiefly from the isoseismals covering portions of San Mateo, Santa Cruz, San Benito, and Monterey Counties, that the intensity diminished much more rapidly to the southwest than it did to the northeast. This interesting fact suggests that, of the two crustal blocks differentially displaced on the fault, the southwest block was perhaps the more passive. It may, however, indicate that the apparent intensity, as interpreted from effects on structures and objects, is a function of the character of the underlying rocks; since on the southwest side of the fault-trace there are extensive areas of highly elastic granitic rocks, while on the northeast side of the fault-trace these granitic rocks are deeply buried by sedimentary formations and appear nowhere at the surface west of the Sierra Nevada.
6. The zones of equal gradation of intensity, ranging from X to VII, are fairly evenly spaced, tho broadening with diminishing intensity; from VII to VI the zone is notably broader, particularly in the northern portion of the region affected; and from VI to II the broadening of the zones is very marked.
The generalizations above set forth are independent of the irregularities in the isoseismal curves associated with the valleys. We may now inquire into the relationship which obtains between the valleys and the distribution of apparent intensity.
The most northerly locality where this relationship appears is on the flood plain of the Eel River, near the coast, in Humboldt County. The lower part of the Eel River Valley has been carved by stream erosion out of a synclinal trough of Pliocene strata having a thickness of over a mile. The syncline is flanked by older and much harder sandstones which are probably of Franciscan age. On the south of the valley these older sandstones constitute a bold mountain ridge, stept with terraces, which terminates in Cape Mendocino. The north side of the ridge has an east and west trend, and the Pliocene strata extend well up on its flanks. There is no suggestion of a fault on this side of the ridge, the trend being determined by the axis of the synclinal fold. The other side of the flood plain has a less regular northwest-southeast trend, converging upon the south side in the vicinity of Rio Dell. The flood plain is thus bounded by a wide trumpet-shaped but asymmetric contour terminating in lagoons and sand beaches south of Eureka. The depth of the alluvium of the flood plain is not known, but the features of the region suggest that it is undergoing subsidence and the alluvium may be several hundred feet thick. On this flood plain the apparent intensity was notably higher than on the surrounding slopes. This is shown by the extent of destruction in Ferndale and other towns situated upon it, and by the rupturing and deformation of the
The apparent intensity of the lower part of the Eel River flood plain grades from X to IX, tho in general nearer IX than X. It is surrounded by a belt of country where the intensity grades from IX to VIII. This belt has a width of a few miles on the Pliocene terrane to the northeast of the flood plain, and probably scarcely extends to the harder Franciscan rocks of the ridge to the south. The facts thus necessitate the recognition on the intensity map of an area of high intensity, including a range from X to VIII, in the midst of a region where the prevailing intensity ranges only from VIII to VII. This, as will be seen in what follows, is typical of all the more important alluviated valleys of the Coast Ranges, and indicates clearly that the apparent intensity for such situations is a function of the underlying formations.
On the more limited flood plain of the Mattole River at Petrolia, the destructive effects were even more intense than at Ferndale, and in marked contrast to those apparent in the few scattered houses on the rocky upland. But little can be inferred from this contrast, since Petrolia is situated on the projection of the fault-trace, and only a few miles beyond the most northerly point to which it has been mapped.
The town of Willets is at the headwaters of a branch of the Eel River on a flat alluviated valley-bottom several miles in extent. The situation and character of the valley are such as to suggest that it is a filled-in lake basin. The ground-water below the valley-floor stands within a few feet of the surface. The town is 26 miles from the coast at Mendocino City, and not less than 30 miles from the fault-trace; yet the apparent intensity was not less than IX of the scale, or equal to that which prevails on the hard rocks in the zone, the distal border of which is usually not more than 6 miles from the fault-trace and often much less. Between Willets and the coast the intensity had diminished from X in the vicinity of the fault-trace to less than VII. This rapid rise from less than VII in the territory immediately to the west, to IX on the valley-floor, with no evidence of other factors intervening, and no evidence of similarly high intensity on the rocky slopes surrounding the valley, again indicates that the apparent intensity is a function of the character of the valley-floor.
A similar condition prevails in the valley in which Ukiah is situated, 20 miles to the south of Ukiah. The physiographic features of the valley are described by Mr. George McGowan in his report describing the effects of the earthquake at Ukiah. The town is about 27 miles from the fault-trace, and in this interval the intensity had diminished from X to less than VII. In Ukiah, which is on the old flood plain of the Russian River, near the middle of the valley-floor, the intensity rose to between IX and VIII. Here again, there can be little doubt as to the influence of the underlying formations upon the destructive effects of the shock. This conclusion is supported by the time at which the shock was felt. Ukiah is one of the few places where satisfactory time observations were obtained.
At the International Latitude Observatory, Dr. Townley reports that he was awakened by the shock and lookt at his watch, finding the time (corrected) to be 5h 12m 30s, and he is of the opinion that the shock commenced at 5h 12m 17s. This accords fairly well with the time the shock was due at Ukiah, and affords no suggestion that the local high apparent intensity may have been due to a local earthquake.
Another valley area of high intensity is on the west side of Clear Lake, extending from Kelseyville to Upper Lake. Lakeport, in the central portion of this area is 36
In general, then, while from the nature of the case it is not possible to deny positively that a local earthquake may have occurred on the morning of April 18, 1906, at the same time as the main shock, no evidence appears to sustain that view. On the other hand the evidence here as elsewhere supports the belief that the apparent intensity is a function of the underlying formations to the extent manifested in this district.
Coming now to Santa Rosa Valley, we encounter an interesting case of high intensity, associated with an alluvial valley-bottom. The valley may be described as an ovalshaped area, extending for 24 miles from Healdsburg to the vicinity of Penn's Grove, with a maximum width of 8 miles on a line lying between Santa Rosa and Sebastopol. The general trend of the central axis of the valley is about N. 30° W. It is thus not far from parallel with the general trend of the fault along the coast. Over a considerable expanse the valley-floor is perfectly even, and appears level to the eye. At its widest portion, however, it has a slope from an elevation of 170 feet above sea-level in the eastern part of the city of Santa Rosa, to about 50 feet above sea-level, a descent of 15 feet to the mile. In this section there are no terraces, but a perfectly even profile. To the north of Santa Rosa, however, the floor of the valley is less even, and it is stept in a few broad terraces, the lowest of which is the present flood plain of the Russian River.
The geomorphogeny of the valley is not altogether simple; the primary fact in its development, however, is that it has been carved by stream erosion to its full width out of a great syncline of Merced (late Pliocene) strata. [2] The upturned edges of these Merced strata, planed down to an even but now somewhat dissected surface, constitute the floor of the upper terrace lying to the north of Mark West Creek at an altitude of about 200 feet above the flood plain of the Russian River. On a somewhat lower terrace is the town of Windsor. South of Mark West Creek, the valley is in general deeply alluviated and the wells a little to the east of the city of Santa Rosa (150 feet deep) show that the alluvium is saturated with ground-water to within a short distance of the surface. The distribution of this ground-water thruout the valley is, however, not well known, no systematic investigation ever having been made. On the western side of the valley from Sebastopol
Now the notably high apparent intensity of the earthquake shock was confined to the alluviated portion of the valley-floor. The 2 centers of population which suffered most severely were Santa Rosa and Sebastopol. At Windsor, situated on the terrace cut in the Merced rocks, the intensity was distinctly lower. Healdsburg, at the northern extremity of the valley, is also on alluvium and the intensity was here again high, tho not quite equal to that at Santa Rosa and Sebastopol. The town of Guerneville, on the old flood plain of the Russian River, below the Santa Rosa Valley, suffered most severely; while the cemetery of the town, but a short distance away, on a rocky terrace 190 feet above the town, was affected in a distinctly less degree, only one monument having been overthrown, and a few moved on their pedestals. The rapid diminution of intensity on passing from the alluvium to the rocky slopes, thus specifically illustrated at Guerneville, is characteristic of the borders of the Santa Rosa Valley. To the east of the city of Santa Rosa, this diminution is so rapid that the gradation of intensity can not be adequately exprest upon the intensity map. Under these circumstances it is difficult to avoid the conclusion that the severity of the earthquake shock on the alluvium of the Santa Rosa Valley is in large measure referable to the character of the ground. Were a local shock a factor in the case, we should expect that the high intensity would not be limited to the alluviated area, but would also be manifested on the surrounding mountain slopes. This expectation not being realized, the hypothesis of an independent local shock stands without support. The general position of the isoseismal curves off the valley-bottoms is not notably affected by the high apparent intensity in the valleys. In arriving at the conclusion that the high apparent intensity in this valley is referable in large measure to the character of the ground, it is not thereby intended to exclude other contributory factors. A theoretical discussion of the effect at the surface of the earth of a concussion at a point within the crust shows that for a certain path of emergence the horizontal jerk of the emerging earth-wave, and, therefore, the destructive effect in general, would be at a maximum. The fact that the earthquake under consideration was due not to a concussion at a point, but to a jar developed by movement on a plane at least 270 miles long, reaching to the surface and of unknown depth, renders the application of this doctrine difficult and of questionable value. Nevertheless, the tendency, which is demonstrable in the ideal case, would also exist in the more complex actuality; and it is by no means impossible that the zone of maximum destruction may fall in a general way within the Santa Rosa Valley, and would thus be a factor conducive to excessive destruction, in addition to the factor inherent in the character of the ground. This suggestion, to have weight, should be corroborated by observations in other portions of the general zone of destructive effects, and it must be confest that satisfactory corroboration is lacking.
While the geology of the Santa Rosa Valley has not been mapped in detail, owing to the lack of topographic maps, it has been carefully studied, particularly from the structural and stratigraphic point of view, by Mr. Vance Osmont, [1] and no fault traversing the valley was found by him. The underlying structure, so far as has been made out, is as already stated that of a broad, rather simple, synclinal fold. It has also been indicated that the surface of the valley has been subjected to recent deformation, whereby the western side
But none of these suggestions, whether of contributory shock, or an unrevealed fault, or of coincidence of the valley with a vaguely defined zone of maximum horizontal jerk, or of sudden relief from synclinal compression, are sustained by satisfactory evidence. They are possibilities which, with the facts before us, it is possible neither to affirm nor to deny. The reference to them in this place is only excusable on the ground that they are suggestive of lines of inquiry which may perhaps be profitably undertaken at some future time. On the other hand, the influence of the character of the ground upon the apparent intensity is sustained by cumulative evidence.
In Sonoma and Napa Valleys, the disposition of the isoseismals is very evidently determined by the contour of the valleys, the high intensities running far up the valleys within areas of lower intensity on either side. In Sonoma Valley the upper and lower parts are alluviated, while the middle part is not; or, if so, only to a slight extent, and it is being trenched by the stream which flows thru it. The floor of Napa Valley, on the other hand, is alluviated thruout, save for some rocky spurs and isolated rocky hills which occur along portions of the sides of the valley. The intensity diminishes in the upper part of Napa Valley, in the vicinity of Calistoga, where the alluvial deposits thin out, notwithstanding the fact that Calistoga is somewhat nearer the fault along the Rift than is Napa City, at the lower end of the valley, and notwithstanding the fact that Calistoga is approximately on the line of the Mount St. Helena fault described by Osmont. If the relatively high apparent intensity of Napa Valley were in any way referable to a local earthquake on a fault traversing the valley, we should not only expect the effects to be manifested on the rocky slopes of the valley, as well as upon its floor, but would also expect higher intensities on the line of the only well-defined fault known to traverse the valley. Neither of these expectations is realized, and upon the slopes of Mount St. Helena, in the vicinity of the fault which traverses its western front, the intensity was notably low—not higher than VI. We are thus again forced to fall back upon the character of the ground as the immediate cause of the high apparent intensity on the alluviated valley-floor, particularly in the lower part of the valley.
Specific and instructive instances of the influence of the character of the ground upon the apparent intensity of the shock are afforded by the cities of Petaluma and San Rafael. Each of these cities is built partly upon rock and partly upon the alluvium of the tidal marshes of the San Francisco Bay. Petaluma is situated at a distance of 14 miles from the fault, and San Rafael at a distance of 9 miles. In both cities the damage to buildings, chimneys, etc., was notably less upon the rock than upon the alluvium, altho the latter can not in either case be supposed to have any great thickness at the base of the hills. (See fig. 64.)
In the city of San Francisco the detailed study of the distribution of intensity, so successfully carried out by Mr. H. O. Wood, affords a conclusive proof of the paramount influence of the character of the ground in determining the high apparent intensities which affected portions of the city. On the made land in the vicinity of the Ferry Building, about 9.5 miles from the fault, as well as on the tidal marsh land, and along Mission Creek and Lagoon, between 7 and 9 miles from the fault, the intensity was X of the Rossi-Forel scale. But on the rocky top of Telegraph Hill, near the ferries, the intensity was scarcely higher than VII. On the sandstone cliffs at Point Lobos, about 3 miles from the fault, it was about VIII; and on the summits of the chert hills in the central
Under similar conditions of ground, the shock was greater nearer the fault; but there was much greater contrast between the damage produced by the shock on the summit of Telegraph Hill and that in the vicinity of the Ferry Building, at like distances from the fault, than there was between the damage near the ferries and that in the immediate vicinity of the fault. Thus, notwithstanding the general tendency of the intensity to diminish with increasing distance from the fault, it seems to be unquestionable that the degree of intensity which prevailed at any locality in the city depended chiefly on whether the underlying formations are firm rock or incoherent material more or less saturated with water. It would even seem possible to discriminate slight differences of apparent intensity on different kinds of firm rock for the same distance from the fault. Thus the chert hills appear to have suffered less disturbance that those where serpentine
In the case of the made land and old marsh land of San Francisco, where the apparent intensity reached X, there can be no question as to possible local shocks, since the excessive disturbance was so strictly limited to the area lying outside of the original shore line and marsh border.
In the low ground about San Francisco Bay to the south of the city, we have another instance, on a rather large scale, of high apparent intensity determined by the incoherent water-saturated condition of the underlying formations. San Francisco Bay in general, and the southern portion of it in particular, lies in an alluviated valley which has been deprest so that its central portion is now below sea-level. This submerged valley-floor passes insensibly into the Santa Clara Valley which encloses it on the south and extends southward between the Santa Cruz and Mount Hamilton ranges. Treating San Francisco Bay and Santa Clara Valley as one physiographic feature, it may be stated, without going into the evidence in detail, that depression and alluviation have both been greater in the southern end than in the northern. This southern portion of the valley constitutes a great artesian basin, and many wells have been sunk in it. The deprest trough is not, however, wholly filled by alluvium, since several wells have past through late Quaternary strata containing marine fossil remains. It would appear, from the sections revealed by these wells, that with the progress of subsidence, marine deposition alternated with alluviation. The deposits, whether marine or alluvial, appear to be incoherent or unconsolidated, consisting of clays, sands, and gravels, in layers of irregular thickness and extent. Many wells have past through several hundred feet of such materials without reaching bedrock. One well, on the edge of the marsh near Alvarado, reached rock at a depth of 730 feet. At the sugar-mill at Alvarado, and at the Contra Costa pumping plant, in the same vicinity, there are several wells from 300 to 400 feet deep, passing thru clay, sand, and gravel without reaching bedrock. At Roberts' Landing there are 2 wells, one 574 feet deep and the other 540 feet deep, which past thru alternations of clay, sand, and gravel, but did not reach bedrock. A well 1.5 miles south of Milpitas past thru 11 layers of gravel aggregating 166 feet and 12 layers of clay aggregating 218 feet — total depth 384 feet — but did not reach bedrock. The wells in the vicinity of San Jose range in depth from 35 to 500 feet as a rule. One well on the bank of Guadaloupe Creek, however, was sunk to a depth of 1,100 feet, but did not penetrate bedrock. A well at Stanford University is in gravel at 412 feet. On the west side of the Bay there are several hundred wells, most of them less than 100 feet in depth, while the deep ones are usually a little more than 300 feet. Wells are even bored in the bottom of the Bay and an abundant supply of fresh water is obtained from them. These brief statements will be sufficient to afford a general idea of the extent to which the valley has been deprest and filled in with deposits as yet unconsolidated. To the south, the rocky floor of the valley appears at the surface in the vicinity of Coyote, 12 miles south of San Jose. Beyond this, however, the valley again opens out and is deeply alluviated.
On the floor of this valley, from San Bruno Mountain southward, on both sides of the Bay, and southward a few miles beyond San Jose, the intensity was abnormally high. On the rocky slopes between the western edge of the valley-floor and the fault, the intensity had dropt from X at the fault to VIII at the base of the hills. On the valley-bottom it again sharply rose to IX. On this ground were Stanford University, Redwood City, San Mateo, the 44-inch pipe of the Spring Valley Water Company, San Jose, Agnews, Milpitas, and Alvarado. On the eastern side of the Bay the intensity of IX did not persist to the base of the hills, but extended only about halfway from the shore line to the edge of the valley. There was therefore a distinctly diminishing intensity in
To the west of the San Andreas fault in San Mateo and Santa Cruz Counties, the apparent intensity diminishes on the firm rocks more rapidly than to the east of the fault, but it rises very notably on the alluvial fan of Pilarcitos Creek at Half Moon Bay, and in the alluviated valleys of San Gregorio and Pescadero Creeks. Going westward down Pilarcitos Canyon, the apparent intensity drops from X at the fault to less than VII within 4 miles of the fault; but along the coastal fringes of alluvium which lie between the hills and the sea, it rises again to VIII at Spanish Town and to IX on the flats below the town. In the valleys of San Gregorio and Pescadero Creeks an apparent intensity of from VII to VIII extends for 4 miles and 3 miles, respectively, into an area of hill lands where the prevailing intensity is from VI to VII. The geology of this region, the Santa Cruz Quadrangle, has been mapped by Prof. J. C. Branner, and no fault is known at Half Moon Bay. Farther south the San Gregorio fault crosses the mouth of San Gregorio Valley and the middle part of Pescadero Valley, with a course parallel to the trend of the coast or transverse to the axes of the valleys. But the high apparent intensity in the bottoms of these valleys can not be referred to a local earthquake due to movement on this fault, since on either side of both valleys, in the immediate vicinity of the fault, it drops to below VII; while a few miles farther south on the same fault the apparent intensity drops to VI.
At Santa Cruz a portion of the city is built partly on a series of broad wave-cut terraces in the bituminous shale of the Monterey series and partly on the alluviated bottomlands of San Lorenzo River. The contrast in apparent intensity in these two portions of the city is marked. In that portion which is situated upon the terraces the apparent intensity ranges from VII to VIII, while on the bottom-lands of the river it rises to from VIII to IX. It thus appears again, from a consideration of these four cases on the coast extending from Half Moon Bay to Santa Cruz, that the character of the material in the alluviated valley-bottoms has exercised a dominant influence in determining the apparent intensity of the earthquake shock, and that there is nothing in the facts to suggest that any other factor has played an important rôle.
The finest illustration of the influence exercised by alluvium in the production of high apparent intensity is that afforded by the valley of the Salinas River and its extension to the valley of the lower portion of the Pajaro River. The Salinas Valley is one of the notable physiographic features of the Coast Ranges. It lies between the Santa Lucia and Gavilan Ranges. It is deeply alluviated and strikingly terraced, particularly in its lower part. The course of the valley was probably determined originally by the fault along the eastern base of the Santa Lucia Range. The river discharges into the Bay of Monterey about its middle part, a few miles south of the mouth of the Pajaro River. On the flood-plain tracts of both rivers, and along the beach of the Bay of Monterey, the intensity was IX. This extended up the river for several miles above the town of Salinas. There were extensive fissures in the alluvium as far as Gonzales, with slumping of the ground toward the river trench. Damage of structures, indicating an intensity
Still farther south in San Luis Obispo and Santa Barbara Counties, far beyond the isoseismal IV, an apparent intensity of IV is indicated by the effects observed in the valley-lands at San Luis Obispo, Edna, Arroyo Grande, Pismo, Santa Maria, Casmalia, and Lompoc. In the flat alluviated valley-bottom in which the town of Hollister is situated, about 8 miles east of the southern end of the fault at San Juan, the apparent intensity rose to IX, but diminished very rapidly on the hill lands immediately to the east of the valley to VI, which appears to have been the normal intensity for the mountainous tract between Hollister and the San Joaquin Valley.
Farther southeast there was a similar but less marked rise in the apparent intensity at Lonoak, Priest Valley, and Hernandez, all of these being on alluviated bottoms.
In the alluviated valleys to the east of the Berkeley Hills, the apparent intensity was abnormally high and the area occupied by these valleys constitutes an isolated area in which the intensity ranges from VII to VIII in the midst of a belt in which the range is from VI to VII. At Pleasanton the intensity was somewhat higher than at Sunol, altho the latter is nearer the fault of April 18, 1906, and is situated, moreover, on the line of an old fault which traverses the west side of Livermore, in the more open part of the valley, where the alluvium is deeper, tho 8.5 miles farther from the seat of disturbance, the intensity was about the same as at Sunol. At Martinez, on an alluviated embayment of Suisun Bay, the damage due to the shock was much greater than in neighboring towns situated on rock, even when the latter were nearer the fault. Beyond Martinez to the eastward there is a very marked bulge to the east of Suisun Bay, in the isoseismal VII, which can be attributed only to the low and marshy character of the ground. The apparent intensity at Antioch was a degree higher in the scale than that at Mount Hamilton, altho it is double the distance from the fault of April 18; and altho there are several old faults in the vicinity of Mount Hamilton and none are known near Antioch.
The influence of the valley-lands upon the apparent intensity is well shown on a large scale in the disposition of the isoscismal curves about the Sacramento Valley. In the mountains to the west of the Sacramento Valley the apparent intensity ranges in general from VI to V; but on the floor of the valley eastward to beyond the Sacramento River, it is very uniformly about VI or VI+.
The most interesting case of high apparent intensity in a valley-bottom remote from the San Andreas fault is that of the San Joaquin Valley. This case merits especial consideration, since of all the valleys here considered it is the one which is most suggestive of the occurrence of a local earthquake, distant from, tho connected with, the main movement on the San Andreas fault. While the suggestion is strong, however, the evidence is not conclusive of the occurrence in this region of a quasi-independent
The apparent intensity on the floor of the Sacramento Valley, as has been stated, ranges about VI + of the scale. This is somewhat higher than at several points in the adjacent Coast Ranges to the west, and the difference is ascribable to the alluviated character of the valley-floor and the water-saturated condition of the alluvium. As we follow the Sacramento Valley southward into the San Joaquin Valley, it converges upon the San Andreas Rift, and we should naturally expect an increase in the intensity by reason of the diminution of the distance from the seat of disturbance. This expectation is in a measure realized by an eastward bulge in the isoseismal VII opposite Suisun Bay, and by the somewhat higher intensity at Tracy and Westley than at Sacramento and Stockton.
Southward from Westley, however, the apparent intensity increases at a rate which can not be referred to the slight approximation of the region to the seat of the main disturbance. At Crow's Landing the apparent intensity is VII; at Newman it is VIII; at Volta it is VIII +; and at Los Banos it is IX. These points lie on the west side of the valley between the San Joaquin River and the flanks of the Coast Ranges. South of Los Banos, on the valley floor, settlements are very few, and information as to the apparent intensity is unfortunately lacking over an extensive territory. At Coalinga, however, the apparent intensity is VII, indicating that the abnormally high figures prevail over the western side of the valley from Crow's Landing to southward of Coalinga, a distance in a north and south direction of not less than 100 miles. That the high apparent intensity was not wholly confined to the valley-floor, but also extended into the flanks of the Coast Ranges, is shown by the remarkable series of landslides which were started by the earthquake for a distance of about 23 miles northwestward from the vicinity of Cantua, reported by Mr. S. C. Lillis, and described by Prof. G. D. Louderback in another part of this report.
Now Los Banos, where the apparent intensity was highest, is distant 40 miles from the nearest point on the San Andreas fault at San Juan, its southern end. It is nearly 34 miles in an air-line from Hollister, the nearest point to the westward having a similarly high apparent intensity. In the Coast Ranges between Hollister and Los Banos, the intensity was as low as V.
These facts are suggestive, as already stated, of a local disturbance at or about the same time as the main movement along the San Andreas fault.
Certain circumstances detract, however, from the force of this suggestion, and indicate another possible explanation which, it must be confest, is not very conclusive in view of the remoteness of Los Banos from the seat of disturbance. The portion of the San Joaquin Valley in which Los Banos lies is undoubtedly an underground water reservoir. It lies at the base of the alluvial fans of the Coast Ranges where the streams sink, and the waters of the San Joaquin River maintain the water-table at no great distance below the surface. As shown by the experiments of Prof. F. J. Rogers, described in another part of this report, water plays an important part under certain conditions in increasing the amplitude of the earth vibrations and, therefore, their destructive effect. In this respect the region about Los Banos would be particularly favorably conditioned for the development of high apparent intensities, as inferred from destructive effects. The general conditions are quite analogous to those in the Salinas Valley, in the bottom-lands of the Pajaro River and the Russian River, and in the region about the south end of San Francisco Bay. The chief difference is in the greater remoteness of the Los Banos region from the seat of disturbance, if only one such seat be assumed.
Another circumstance which weakens the suggestion of a local earthquake is the failure of the isoseismals below VII to carry out the suggestion by bulging into the Coast Ranges on the west or the flanks of the Sierra Nevada on the east. In the latitude of Los Banos, the high apparent intensity was confined to the valley-floor, altho farther south, near Cantua, this can not be affirmed. In view of the experiments of Professor Rogers, it seems probable that in the near future, by an active prosecution of such experiments coupled with close field observation, we shall arrive at an arithmetical expression for the coefficient which will enable us to reduce the apparent intensity of water-saturated alluvium to the true intensity due to vibration in homogeneous elastic rock. When that coefficient becomes available, it will perhaps be possible to determine whether or not the destructive effects exemplified in the San Joaquin Valley at Los Banos are referable to the conditions of the ground or to a local seismic disturbance. Until then the question must remain an open one. Analogy with other valley lands nearer the fault, where high apparent intensities are referable, both on the field evidence and in the light of Professor Rogers' experiments, to local conditions, militates against the hypothesis of a quasi-independent earthquake. The remoteness of the region from the known fault and the high intensities on the flanks of the Coast Ranges indicated by the new landslides at Cantua, favor that hypothesis; but no positive conclusion can be reached at present.
Altho the geology of California has been studied in detail at but few localities outside of the gold belt of the Sierra Nevada, yet the general reconnaissance work that has been done by various geologists has brought to light many of the important faults in the state. Such as are known are indicated on map No. 1, without any attempt to discriminate between the varying degrees of certainty with which their existence has been determined. The map serves the double purpose of bringing together for the first time our knowledge of the distribution of faults thruout the state, and of illuminating a brief discussion of the relation of apparent intensity to fault-lines. On 4 of these faults there have occurred 5 severely destructive earthquakes within the last 50 years. It thus behooves students of Californian seismology to become familiar with these structural features of the state. A recent account of the Calabrian earthquake of September 8, 1905, dealing particularly with the distribution of intensity, [1] and the relation of that distribution to fault-lines known or inferred, gives an especial interest to the consideration of the faults of the Californian region at this time. In the preceding section of this report, it has been shown very definitely that abnormally high apparent intensities were developed on the valley-bottoms, and the cause of this has been referred in a general way to the incoherent and water-saturated condition of the materials underlying these valley-bottoms. In Calabria, in the account referred to, Professor Hobbs correlates the zones of exceptionally high intensity with lines of ancient faults, which in some portions of the region are known on geological evidence to exist, and in others are supposed to exist because of the high intensities manifested. He does not recognize the character of the underlying formations as an important factor in producing different degrees of intensity, as inferred from destructive effects at the surface. In this respect his conclusions do not harmonize with those arrived at in the study of the California earthquake of April 18, 1906. It thus becomes a matter of interest to ascertain what, if any, influence was exercised by the known faults of California, other than that which was the seat of disturbance, upon the distribution of apparent intensity, independently
In southern Oregon and in northeastern California, in Modoc, Shasta, Lassen, and Plumas Counties, the shock was so uniformly feeble that there is no suggestion of locally high intensity due to any cause. The same general statement is true of northeastern California, in Del Norte, Siskiyou, Humboldt, and Trinity Counties; but in this region some of the faults, particularly that of Redwood Mountain, were not farther from the seat of disturbance than certain localities farther south, where abnormally high apparent intensity was developed on valley-bottoms. If the Redwood Mountain fault had been a locus of movement, there can be little doubt, altho the settlements in that region are few and scattered, that we should have heard of the severity of the shock. No evidence, however, has come to hand indicative of any exceptional severity on or near the line of that fault.
Along the eastern front of the Sierra Nevada, from Honey Lake and the Taylorsville district to Tejon Pass, altho there are many extensive faults, and altho on one of these there occurred a movement which caused the Inyo earthquake of 1872, yet there is no suggestion of any local movement on any of these on the morning of April 18, 1906. The intensity of the shock along this general fault-zone was about IV of the scale; but the movement was a slow, gentle swing characteristic of a heavy distant shock.
Similarly, the numerous faults which traverse California south of Tehachapi may be left out of consideration, no shock at all having been felt over the greater part of the region, and but feebly in those parts where it was felt.
There thus remain of the faults in California practically only those that fall within the zone of destruction, to merit serious consideration. The most northerly of these is the Mount St. Helena fault described by Osmont. [1] This fault has a northwest-southeast strike, and a throw of not less than 2,000 feet. It forms a well-marked and little-degraded scarp on the southwest side of the mountain and the date of its principal movement is within the Quaternary period. The projection of this fault to the northwest is not known; to the southeast it undoubtedly passes beneath the floor of Napa Valley, in the vicinity of Calistoga. Neither on the slopes of the mountain nor at Calistoga was there any evidence of abnormally high intensity, and the necessary inference is, therefore, that there was no movement on the fault at the time of the earthquake.
The southwest front of the Berkeley Hills, and the extension of the same geomorphic feature farther south, forming the southwest front of the higher Mount Hamilton Range, is with little question a fault-scarp, or series of scarps, of Quaternary date, now more or less dissected and degraded. The northern extension of the fault-zone beyond San Pablo Bay is not known. It probably contributed to the definition of the western side of the ridge between Sonoma and Petaluma, but apparently did not traverse the middle part of Santa Rosa Valley, since the study of that region by Osmont failed to reveal it.
This fault-zone is of peculiar interest from the point of view of the present discussion, since it appears to have been the seat of disturbance of the earthquake of 1868. At that time the fault-trace was marked by a crack at the surface, which was traceable for 20 miles or more along the base of the scarp slope, altho the amount of the movement was probably quite small. The trace of the fault is approximately parallel to the San Andreas Rift, and is 18 miles distant from it. As has already been suggested, this fault would seem a priori more succeptible to the influences which would make for renewed movement than most other faults of the region. But there is no evidence that any movement occurred upon it. The intensity showed no abnormal increase along
The fault which is so well exposed in the sea-cliff south of Fort Point traverses the city of San Francisco in a southeasterly direction for an unknown distance. Along the line of its probable course, Mr. Wood has noted evidence of an increase of intensity. The fault in its projection seaward probably intersects the San Andreas fault beneath the Gulf of the Farallones. It is therefore possible that there was some slight distribution of the movement along this intersecting fault.
The San Bruno fault-scarp, on the peninsula of San Francisco, south of the city, is well illustrated in Plate 15, and its structural relations are described in a paper by Andrew C. Lawson on the Geology of the San Francisco Peninsula. [1]
The base of the scarp is from 2.5 to 3 miles distant from the San Andreas Rift, and is nearly parallel to it. The fault is in two parts: a main fault with a throw of not less than 7,000 feet, which drops the Merced (Pliocene) strata against the older Franciscan rocks, and an auxiliary fault which drops a wedge of Franciscan strata between the main fault and the mass of San Bruno Mountain. The town of South San Francisco is on the lower slopes of a rocky spur of San Bruno Mountain, between the two faults, i.e., it is on the dropt wedge of Franciscan rocks. In the water-saturated alluvium and sands of Merced Valley, the apparent intensity was high, ranging up to IX of the scale; but in South San Francisco, on rock foundation, it was notably lower, as appears from Mr. Crandall's report. The situation of south San Francisco, between the two faults, is such that had a movement occurred on either, the damage to structures would have been accentuated. But the fact is that the damage was not so accentuated, and there is thus no warrant for supposing that any local fault movement occurred.
One circumstance which, upon first thought, seems to contravene this conclusion, was the sudden outgush of water at one point at the base of the San Bruno scarp. This remarkable occurrence is described in another place, but may be mentioned here, for the purpose of bringing together the facts bearing on the question. The water issued, as near as can be determined, at a point on the slope immediately above the fault-trace of the auxiliary fault, in the underlying hard rocks, which are there mantled with an unknown thickness of sand, possibly 50 feet or more. The outgush of water is indicative of sudden compression of incoherent water-saturated sand, and does not necessarily imply a movement on the deeper fault. Along the line of the fault there are longitudinal depressions, and it is suggested that one of these was filled with sand, under conditions which did not permit of rapid drainage; so that the sand was saturated with water, which was expelled as the compressive wave traversed the locality.
In the region to the southwest of the San Andreas Rift in San Mateo and Santa Cruz Counties there are several faults, most of which are represented on maps Nos. 21 and 22. No evidence of movement has been detected on any of them, altho the territory has been examined quite closely; nor does their presence appear in any way to have affected the disposition of the isoseismal curves. They nearly all traverse a country occupied by rocky mountainous slopes, and have considerable variation in orientation, altho the prevailing strike is northwesterly and southeasterly. One fault, however, viz., the San Gregorio fault, crosses 2 valleys — San Gregorio Valley and Pescadero Valley — in which the intensity of the shock was abnormally high. The independence of this high apparent intensity to the fault has been pointed out in another place.
To the north of Black Mountain, on the northeast side of the San Andreas Rift, a branch fault leaves the Rift line a little south of Portola, at an angle of about 25°, and is traceable for about 8 miles on the lower northeastern flank of Black Mountain. Between this Black Mountain fault and San Andreas Rift there is enclosed a wedge of
In the Mount Hamilton Range, between Niles Canyon and Mount Hamilton, there are many faults; but none of them, so far as the information available will warrant a conclusion, appears to have affected in any way the distribution of intensity. Two of these, the Mission Peak fault, which is probably a branch from that on which cracks opened in 1868 near Haywards, and Mission Creek fault, pass close to the town of Niles. But the apparent intensity at Niles was less than on the flat alluvial tract to the west, and not greater than in the valley-land about Pleasanton and Livermore to the east; and this circumstance amounts to a proof that no movement occurred on either of these faults. A similar conclusion may be drawn with reference to the Sunol fault, from the fact that the apparent intensity at Sunol was somewhat less than at Pleasanton, altho the former is nearer the Sunol fault than is the latter. In the country between the Haywards fault and the Sunol fault there are several minor faults, but there is no indication in the distribution of intensity of movement having occurred on any of them. Similar statements are true of the fault zone extending from the vicinity of Benicia northward on the west side of the Sacramento Valley.
In the canyon of Pajaro River, below Chittenden, there is an east-west fault whereby the Tertiary rocks on the north side have been dropt against the granitic rocks of the Gavilan Range on the south. This fault crosses the San Andreas Rift, and its known extent on either side of the Rift is within the zone of high intensity referable to the movement of April 18. There are here no especial features in the distribution of apparent intensity which suggest any movement on this fault. It is possible, however, that a slight movement took place on this fault, since the steel bridge over the Pajaro River, which is about on the intersection of the two faults, was distended 3.5 feet between its end piers, as shown in plate 65B, in a way that can not be altogether satisfactorily explained by the movement on the fault along the Rift. The direction of the chief displacement of the piers was about midway between the strikes of the two faults.
In the Santa Lucia Range to the southwest of the Salinas Valley, there are several faults. The principal one runs along the northeast flank of the range on the edge of the Salinas Valley. The reasons for ascribing the high apparent intensity on the floor of the Salinas Valley to the character of the underlying formations, rather than to any
To the southwest of this is another parallel, but a longer fault, along the southwest side of the San Rafael Mountains. In the valley lands to the southwest of this, about San Luis Obispo, Edna, Arroyo Grande, and Santa Maria, the intensity rose from III to IV; but in view of the accumulation of evidence set forth in the preceding pages as to the influence exercised by alluviated bottoms upon the apparent intensity, this rise is more probably referred to the character of the ground than to proximity to this faultline. South of Santa Maria is a region of frequent seismic disturbance, but no sharp shock of a local earthquake was felt there on April 18.
It thus appears that in the territory extending from Humboldt County to Santa Barbara County, while there are about 40 faults known to geologists who have studied the region, there is no evidence of movement on any of them except in 3 cases. One of these is a branch from the fault-zone of the San Andreas Rift — the Black Mountain fault; another is a transverse fault intersecting the Rift in Pajaro Canyon; and the third is the fault which traverses the city of San Francisco and probably intersects the San Andreas fault beneath the Gulf of the Farallones. In these cases it is possible, in the light of the evidence, that some portion of the movement on the main fault was distributed along intersecting faults.