Visible Undulations of the Ground

The earth-waves generated at the fault past thru the earth's crust with a velocity of probably from 2 to 3 kilometers per second. The undulations of the surface due to the passage of such waves would be so swift that they would scarcely be observed visually. Yet there is considerable testimony, of a consistent and independent character, that much slower undulations were observed. This testimony comes from various parts of the region disturbed, and a great deal of it is positive and unequivocal as to what seemed to be the fact. The evidence indicates that there is a type of wave in the ground, in the region of high intensity, which has not yet been sufficiently recognized, and the origin of which is obscure. Some 20 or more observations bearing upon this class of phenomena are here summarily recorded:

Judging from the descriptions given, these waves behaved like undulations in water, with an oscillation approximately normal to the surface. They were for the most part observed on alluvial tracts, but some of the reports come from districts where there is but a thin veneer of alluvium or soil upon the rocks. If it should prove, on the basis of more abundant evidence, that these waves are peculiar to alluviated basins, they may be explained as reflections from the rocky slopes of such basins. If a bowl of liquid be tapt smartly, vibrations are inaugurated in the rigid bowl which have a speed so great that the secondary waves generated in the liquid pass out from all parts of the walls of the vessel sensibly at the same instant. But the secondary waves thus generated in the liquid have so slow a rate of propagation that they are quite apparent to the eye, and in the central part of the surface of the liquid, when the waves meet, there is a violent commotion. If, instead of a bowl of liquid, we have a rock basin filled with water-saturated alluvium, it seems probable that a similar effect would be produced in a modified degree; and the visible waves at the surface may have had such an origin. But whatever be their origin, it is apparent that they must be a large factor in damaging structures situated upon the ground in which they occur, and so raising the apparent intensity on any scale based on destructive effects.

Freshwater, Humboldt County (S. E. Shinn). — My orchard raised up between 2 and 3 feet like a big breaker coming in.

Ferndale, Humboldt County (A. W. Blackburn). — Those who claim to have been out of doors when the shock came, state that the earth rose and fell like the waves of the sea.

Fort Bragg, Mendocino County (O. F. Barth). — A man walking along the street was thrown down. He is positive the wave traveled southwest. The ground undulations were 2 and 3 feet high.

Point Arena, Mendocino County (W. W. Fairbanks). — The ground moved in undulating swells or waves, rising and falling.

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Santa Rosa, Sonoma County (Miss Locke). — A man saw an earth-wave 2 feet high.

Cotati, Sonoma County (C. L. Jeffrey). — The surface of the earth waved like water.

Napa, Napa County (T. Hull). — Those who were out of doors say the trees bent as the shock came like a wave of the occan.

Pleasanton, Alameda County (Miss F. Locke). — A lady near Pleasanton saw the earth go in waves like the ocean.

San Francisco (Miss F. Locke). — A fireman at the engine house 1757 Waller Street said the ground went in waves.

San Mateo, San Mateo County (Mr. Maxwell). — The earth rose and fell like the swell of the sea, the swells being about 3 feet high.

Saratoga, Santa Clara County (Louise M. Atkinson). — Distinct waves past over the ground from northwest to southeast, the orchard trees rising and falling on each wave, like ships at sea, while the electric poles along the road leaned this way and that, some seeming almost to touch the ground.

Santa Clara, Santa Clara County (I. H. Snyder). — Mr. Dan Pickering, living a mile south of Santa Clara, says that the ground rose and fell in waves about a foot high. Others say that the orchards seemed to be agitated by a wave-like motion.

San Jose, Santa Clara County (W. S. Prosser). — 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 much less, but they must have been greater, for there is no evidence which shows any such vertical cracks as would have been produced by short waves. A good observer 6 miles southwest of San Jose described the waves as parallel with certain tree rows which are northeast and southwest; and the waves moved from him at right angles to the line toward San Francisco. Another person, 6 miles northwest from San Jose and looking south, saw the waves (which he thinks were east and west) coming toward him, and hence toward San Francisco; but about the middle of the quake these were met by other waves and the whole surface resembled hillocks or cross seas, and the tree-tops waved wildly. To the man to the southwest of San Jose, however, the tops of the trees were almost still, while the trunks waved sinuously.

Meridian, Santa Clara County (G. A. Waring). — A lady reports seeing waves traveling southward along the driveway, and a man reports seeing a heavy wagon move back and forth several times, 4 or 5 feet along the driveway.

Campbell, Santa Clara County (F. M. Righter). — People out of doors at the time state that there was a very rapid wave-like motion of the surface of the earth.

Wright, Santa Clara County (Flora E. Beecher). — Mr. Deacon, our neighbor, rose and stood by the window, and he declares that the ground rose in waves.

Coyote, Santa Clara County (G. A. Waring). — Near Coyote a man reports having seen a northwest-southeast fence move in a wave-like motion, beginning at southern end.

Paicenes, San Benito County (G. A. Waring). — Toward the Cienega Lime Kilns, 4 miles south of Paicenes, a man reports seeing a wave coming westward thru a grain field.

San Lucas, Monterey County (G. A. Waring). — West of San Lucas the waves were reported to have been seen moving southward over the hills.

San Luis Ranch, near Pacheco Pass (G. F. Zoffman). — Mr. Mills stated that the surface of the ground moved up and down like the waves of the ocean.

Mendota, Fresno County (G. F. Zoffman). — The people who observed the plains at Mendota said that they assumed a wave-like appearance, and that the trains rose and fell as the undulations past beneath the tracks. They also stated that this wave-like appearance was confined to the north and south movement, the east and west motion being more in the nature of a tremor.

Visalia, Tulane County (F. A. Swanger). — The movement of swell and fall of wave seemed strong.