The Bancroft Library
Seismology in the United States
By Andrew C. Lawson
The issue of the first Bulletin of the Seismological Society of America appears to me to be a fitting occasion for a brief review of the present status of seismology in this country, and for some suggestions looking to the possible improvement of that status.
The great advances in seismology in recent years have been along the lines of instrumental perfection and the interpretation of instrumental records. The wide distribution of modern seismographs in civilized countries has supplied the data necessary for important discussions of the significance of earth vibrations, their rate of propagation and their paths; and these discussions have not only greatly enriched the science of the earth but have drawn many new men to this field of research.
Until within a very few years the United States was far behind many other countries in its equipment for this work and in the number of men interested in it. The list of seismological stations published in another part of this Bulletin clearly shows, however, that we are bestirring ourselves and are preparing to do our share in the study of earthquakes. This awakening interest in the phenomena of earthquakes dates chiefly from the California earthquake of 1906. It is manifested not only in the establishment of seismological stations at various universities and colleges throughout the country, among which the Jesuit colleges are the most notable for the zeal and thoroughness with which they have extended and organized such installations, but also by the establishment of a society wholly concerned with the advancement of this branch of science.
There is an important department of seismology which can be pursued to advantage only by world-wide cooperation. I refer to the instrumental study of earthquakes of the first class or those of such great violence that their vibrations extend to all parts of the earth's surface and may be recorded by suitable apparatus. The exact
In view of our increasing number of observing stations there can be little doubt but that we shall be able in future to contribute more and more to this world-wide cooperation. Indeed, most of the installations of recent years in this country are better fitted for this kind of observation than for the study of earthquakes of smaller magnitude but of greater local importance.
Now, when we stop to review the spread of these installations in the United States during the past few years, we cannot fail to be impressed with the fact that it is due to local spontaneity and that the distribution of the stations is governed by no guiding principle. Their position has been determined by accident rather than by design. For the purpose of a world-wide network of stations equipped primarily for recording shocks of the first class, they are too few in the greater part of the country and possibly unnecessarily numerous in certain other parts where institutions and interested men are not widely spaced. Under existing conditions the disproportion in the spacing of stations is likely to continue and to become more marked by the multiplication of installations where they are least needed. It is evident from this state of affairs that our seismological activities are unorganized. The lack of organization has been fully recognized by the men most interested in the subject, and various attempts have been made to reduce the work to a more systematic and economic basis. It has been proposed, for example, that at certain of the more important stations of the U. S. Weather Bureau suitable seismographs should be installed and placed under the care of the local officers of the Bureau. This proposal was urged upon Congress by a committee of the American Association for the Advancement of Science, and was endorsed by the chiefs of the more important scientific bureaus of the government. The proposal was, however, rejected.
Another appeal was made to Congress to establish a bureau of seismology under the Smithsonian Institution, and altho the suggestion received the approval of a great many scientific men thruout the country, and altho the subvention asked for in support of the bureau was not more than $20,000, the bill which was introduced for the purpose was killed in committee.
It is clear that if the matter is left to individual initiative or to institutions of local scope that the present unorganized condition of this work is likely to continue. Apparently the only hope for the cure of the evil is that the work should be taken up by a financially strong institution like the Carnegie Institution of Washington.
Another and rather different phase of seismological work and one which has received but little attention in this country is that which is concerned with seismicly active regions. There are several such regions in this country, but the most notable is comprised within the borders of California. In such regions where small earthquakes occur frequently and disastrous shocks occasionally, the proper investigation of the conditions which obtain in the earth's crust necessitates a combination of geological field work with instrumental observations recorded at numerous stations equipped with machines for recording light shocks rather than heavy ones. These numerous stations distributed over such a seismicly active region require the direction of a central station for the region. The work requires a corps of observers who shall give about an hour daily to the apparatus and the forwarding of reports to the central station. It requires also a small number of active field geologists who are specialists in structural and physiographic geology. Such an equipment of stations and men can only be secured by an expenditure of the necessary money for installation, maintenance and salaries. The work thus organized would result in not only the precise location of all the various faults which by recurrent movement produce earthquakes within the region, but it would also enable us to become familiar with the progress of fault movements and so contribute very greatly to geological science.
For such an undertaking, having to do with natural conditions and processes which affect humanity so seriously, it might be supposed that funds would be readily forthcoming. But such is not the case. In the present state of public opinion in California for example, it is practically impossible to secure state aid for the study of earthquakes. The commercial spirit of the people fears any discussion of earthquakes for the same reason as it taboos any mention of an occurrence of the plague in the city of San Francisco. It believes that such discussion will advertise California as an earthquake region and so hurt business. In this state of public opinion our only hope for the proper prosecution of the study of earthquakes in those regions where their study may be most advantageously undertaken is to have the work carried out by an independent and financially capable institution devoted to scientific
A further necessity of a proper organization of seismological investigation is a central bureau of national scope for the systematization and coordination of earthquake reports from all parts of the country, whether they have reference to earthquakes of the first class or those of only regional importance. Such a clearing house cannot be maintained by any local institution, and could only be successfully operated by an institution charging itself with the care of the whole field.
Another phase of seismological research which would be greatly advanced by a proper organization, such as might be effected by the Carnegie Institution, would comprise those studies which are necessary on the occurrence of a first class earthquake anywhere within our borders. Such great shocks do occur from time to time, and the phenomena which are their concomitants must be observed promptly and carefully by competent observers. At the present time there is absolutely no provision for such work. When such a shock does occur, as in the case of the Charleston and California earthquakes, valuable time and effort that should be given to scientific enquiry are devoted to a scramble for means wherewith to do the work.
Besides all this, we need in such an organization as is contemplated a small staff of men concerned chiefly with the theoretical aspects of the subject,--the discussion of the data from the physical and mathematical point of view. There is also needed very urgently an experimetnal laboratory for the purpose of investigating many questions that arise in the study of earthquakes and their destructive effects.
These various phases of this work and others that might be suggested are likely to remain undone until we have effected some kind of an organization properly financed and devoted to this particular field. State aid appears to be remote. The Seismological Society is financially weak, and its chief function will be that of educating public opinion and stimulating private effort. Under these circumstances an appeal to the Carnegie Institution to take up the work of organizing and prosecuting seismological research in this country seems to be well justified. The recent large addition to its foundation encourages the hope that the Institution may be able to do this without detriment to its other large and important undertakings. The assumption of the work by the Institution would certainly meet with the approval of the scientific men of the country.
Suggested Organization for Seismologic Work on the Pacific Coast
Suggestions made at the meeting of the Seismological Society of America held at San Francisco, January 9, 1909.
By J. C. Branner
Under the topic "faults," Professor J. C. Branner was called upon and spoke as follows:
In speaking about faults I beg the forbearance of the chairman and of the members present if I fail to confine my remarks strictly to this particular topic. It is not possible for me to stay to the end of the meeting, and as these meetings are as yet far apart and at uncertain intervals, I want to use this opportunity to offer a few suggestions looking to the best interests of the science in which we are all deeply interested.
Every geologist admits the seismologic importance of faults. This importance has been so clearly demonstrated that, so far as I am aware, no one questions it. There may be earthquakes that are not due to faulting, but we are all familiar with the amount and nature of the evidence showing that the great California earthquake of 1906 was due to movement along a fault line. But it is important to note that geologists know of a great many faults which are not now centres of seismic disturbances. Such faults probably caused earthquakes at some time in the past, but they are now recemented, as it were, and, from the point of view of the seismologist, are inactive and unimportant. In the portion of the coast ranges with which I am most familiar there are literally thousands of faults, if we count both big and little. On the other hand there are probably faults so obscured by soil or by recent deposits, especially along valley floors, that we are unable to say just where they are; and there are still others that are but ill defined at the surface, or the geology of the region in which they occur may not have been studied. Indeed, one of the great difficulties that we have to face in studying earthquakes on this coast is the lack of detailed and trustworthy geologic maps.
Evidently then, and looking at the matter from the point of view of the seismologist, there are faults about which we need not concern
The displacement along the San Andreas-Stevens Creek fault at the time of the earthquake of 1906 was so readily traced from point to point, and the topographic emphasis of the entire fault line was so pronounced that it is highly probable that that particular fault would have been promptly located, even if we had not previously known anything of the geology. But the cases are not always as simple as this one; and even if they were, we cannot afford to wait for such serious disturbances to wake us up to a realizing sense of our duties.
In connection with this subject of faults or epicentra, I believe that the most important work this society can undertake is to organize at once and to put into active operation a permanent and comprehensive system for collecting seismologic data. Only by such means can we hope to ascertain the locations of seismologically active faults as distinguished from the inactive ones. It naturally occurs to one that this could be done by the use of a large number of seismographs judiciously located and carefully looked after. But however important and helpful seismographs and properly equipped seismographic stations may be, their great expense puts them practically out of the question for a young organization with limited means. There is one excellent kind of a seismograph, however, that we can all use to great advantage if we will only set about it, and will take the trouble to put the records on paper and send them in. I refer to our own bodies. Earthquake scales are all based upon personal observations and impressions, and this facilitates the prompt classification of earthquake intensities. And in this matter of location of epicentra the determination of the distribution of intensities is exactly what is needed--for the present at least. In order to make work of this kind effective there should be a large number of observers widely distributed over the area studied, and their results should be made immediately available.
If you will look at the map of California showing the distribution of the stations of the U. S. Weather Bureau, a method of collecting and handling such data immediately suggests itself. Here is an organized body of men accustomed to make certain observations in a systematic manner, and to report them every day to the central office. There are 290 of these weather bureau stations in California alone. Clearly this number of observers is not nearly large enough
These reflections lead me to make the following suggestions regarding a method for getting active observations organized without further delay:
- That, in order to gather data, the society make special efforts to greatly increase its membership in this state and along this coast, and that members be sought with some reference to geographic distribution.
- That the society request all of its members to note the time and intensity of all earthquake shocks felt by them, and to send these notes to the compiler with the least possible delay.
- That the society have the Rossi-Forel scale printed and sent to the members so that each one can have it at hand in order to determine intensities and to accustom him to its use.
- That Professor McAdie be made, ex-officio, the society's official compiler of earthquake data for the Pacific Coast of North America.
- That the society become financially responsible for such clerical help as the compiler may require in connection with this work.
Such an organization as is here suggested ought to place in the hands of the compiler data for the construction of an intensity map of any considerable earthquake within forty-eight hours after the shock. I believe the gathering of such data and the construction of such maps will soon enable us to locate the active faults or centres of seismic disturbances. We shall thus be in position to serve the public by indicating the lines or localities where serious disturbances are most likely to occur and those where they are least to be expected. And all this can be done by cooperation, with the expenditure of very little money, and with the least possible amount of exertion. Expensive seismographs and skilled mechanicians are not required, and the writing of the brief reports here suggested need not take five minutes of a member's time.
I doubt if the plan here suggested would be practicable in a
In what I am here suggesting I make no attempt to cover the grounds of the possible activities of this society. There is much to be done in the way of field observations, of laboratory investigations, and of philosophic deductions. With observations made and work done I am sure the interest of the members of the society will grow, and we shall soon spread our energies into other parts of the field.
Seismological Observations of the Future
By Alexander McAdie
We constantly hear expressions of amazement in connection with wireless telegraphy. The transmission of intelligence over great distances and especially over the sea, without the aid of wires or cables, appeals strongly to the imagination; and few achievements of modern science have aroused so much interest and enthusiasm. The ability to receive information from distant and inaccessible points is indeed significant. But think for a moment, is not this precisely the function of a seismograph? Originally devised and intended as a means of recording the time of a local disturbance, the instrument has been so improved and its use so extended that it now serves, exactly as the receiver of a wireless outfit, to tell of conditions at a distance. Instead of an electro-magnetic wave in the unknown ether, we employ as a medium of transmission the earth itself; and for messengers, the various waves originated by the disturbance.
It is evident that as the seismograph is developed further and the laws of transmissibility of earth waves are determined, we shall acquire extensive and detailed knowledge of what is going on in the earth's crust near the surface, at all centers of activity. In other words, the seismological observatory of the future promises to become a repository of data concerning the earth as a whole. Such data will be of direct value to man in his daily life. Heretofore we have been unaware of disturbances in uninhabited and inaccessible portions of the earth; but
One can hardly imagine a more fascinating line of scientific work than interpreting seismograms, deciphering these records of earth change at far distant points. And as through the spectroscope, astronomy has in recent years been developed chiefly along astro-physical lines, so geology through the seismograph and its auxiliary will make marvellous development along geo-physical lines.
Indeed it is not looking far ahead to conceive of central observatories with a tri-sided organization whereby modern developments in geology, astronomy and meterology can be correlated. These three fields are becomming more and more closely allied and there are certain problems pressing for solution to-day, especially in connection with planetary atmospheres, which require work in all three fields. In two of the fields, astro-physics and aero-physics, great advances have been made within the last five years, and we ahve the promise of a glorious future in these directions. One can have little hesitation in saying that a modern geophysical observatory at some point on the Pacific Coast would mean a wonderful development of knowledge that in a certain sense would be of more direct value for the welfare of mankind than even knowledge of the stars or of the air.
Remarkable Earthquakes in Central New Mexico in 1906 and 1907
By Harry Fielding Reid
Between July 2, 1906 until well into the year 1907 scarcely a day passed that slight shocks or tremors were not felt at Socorro, in the middle of New Mexico, and in its vicinity; and shocks severe enough to do some damage occurred on July 12th and 16th and on November 15th. The series was inaugurated by smart shocks at 3:15 and 3:30 a.m. on July 2d, felt probably everywhere within fifty miles of Socorro. At Socorro they were strong enough to upset small objects (VI) The Roman numerals indicate the intensities according to the Rossi-Forel scale, see page 32., and at Magdalena, twenty miles west, somewhat less strong(V). Six shocks were reported in Magdalena between 3 and 4 a.m. and ten shocks in Socorro between 3:15 a.m. and noon; tremors continued during the afternoon and night. On July 7th smart shocks were felt at Socorro at 1:30 and 4:10 a.m. and at Magdalena about 3 a.m. (All times are in Mountain Standard Time, seven hours slow of Greenwich mean time.)
On July 12th came the first severe shock at 5:15 a.m. which lasted from fifteen to twenty seconds at Socorro (VIII). The walls of many adobe houses were cracked and some brick chimneys were thrown down. Many boulders were shaken down upon the branch railroad to Magdalena a few miles west of Socorro, breaking one rail and a number of ties. The following places report having felt the shock: Socorro, and small towns nearby (VIII); San Antonio (VII-VIII), Elmendorf, sixteen miles south of Socorro, and Carthage, sixteen miles southeast, (VI-VII), San Marcial (VI), Rosedale (IV?), Alamagordo, Silver City, Lake Valley (III-IV), Albuquerque, El Paso (III). It was also felt on the ranches to the east and southeast of Socorro. A slight shock was reported from Fort Wingate about 5 a.m. on July 11th; it is probable that this is an error and that the shock was felt on the 12th; Socorro reports only very slight shocks on the 11th and no other place reports any. The following towns report
The second severe earthquake came on July 16th. Slight shocks were felt in Socorro on the previous night and a sharp one at 6 a.m. (VI?), another slight one at 10 a.m., and three strong shocks at 12 noon, 12:05 and 12:08 p.m. Lighter shocks were felt at 12:30, 1, 1:30, 2:40, 3, 4:10, 6, 8:45, 10, and 11:20 p.m., also on the 17th at 1, 3, 4:20 and 6 a.m., and more on the succeeding days.
The midday shocks of July 16th were slightly stronger than the shock of the 12th. They upset more chimneys, cracked more houses, and threw out some brick gables in Socorro, made a few cracks and overthrew a few chimneys in San Antonio and increased the apprehensions of the inhabitants. Many of the people of Socorro left their houses and lived in tents, not in general because the houses were so badly damaged, but from fear of more severe shocks which might bring the houses down upon them. The Socorro Hotel, a brick building in the eastern part of the town was abandoned on account of the injuries it had sustained, and the majority of the houses of the town suffered some damage. The southeast corner of the brick post-office was thrown out, and its eastern wall bulged; the court house and the high school lost several chimneys; but the School of Mines building, about one mile from Socorro, was not injured. A crack appeared in the adobe walk near the station, but this was insignificant, and apparently not due to the earthquakes but to drying during the hot weather. The hot springs near Socorro did not have their temperature increased as reported. Sensational accounts were published in the papers a few days later stating that Socorro was in ruins, that the inhabitants were fleeing and that a drenching rain had increased the misery. These accounts were so exaggerated as to be practically untrue; a few persons left Socorro, and the rain was unimportant.
The shocks of the 16th were felt practically over the same region as the shock of the 12th and were reported as follows: Socorro and neighborhood (VIII), San Antonio (VII-VIII), Sabinal (V-VI), Rosedale (V), Hillsboro (IV-V), Peralta (IV), Datil (IV?), Albuquerque, Rincon, El Paso (III-IV), Alto, Lake Valley, Fort Bayard (III). The shock was reported as felt at Raton, 235 miles from Socorro to the northeast, and at Douglas, Arizona, 250 miles to the southwest,
Light shocks and tremors continued to be felt almost daily in the vicinity of Socorro, San Antonio and Magdalena with somewhat sharper ones on July 25th at 11:50 a.m., and 30th at 3 p.m., August 5th at 11:20 p.m., and 21st, at 3:30 a.m., October 12th at 1:45 p.m., and 23d, at 11:30 p.m., November 4th at 8 p.m. and December 19th at 5 a.m.
The severest shock of the year occurred on November 15th at 5:15 a.m. and was felt generally throughout central New Mexico. It increased the damage already done in Socorro, but was not much more severe than those of July 12th and 16th. Peralta reported a lighter shock at 2:10 a.m. and about thirty light shocks were felt in Socorro in the course of the day.
The intensity at various places was as follows: Socorro (VIII), San Antonio (VII+), Magdalena, Sabinal (VI-VII), Rosedale, Peralta, Laguna (V), Datil (V?), Hillsboro, Lake Valley, Alamagordo, Willard, Carpenter (IV), Albuquerque (III-IV), Estancia, Torrance (III+), Santa Fe, Cerrilos, Rosewell, El Paso (III), Las Vegas (III?). These have been entered on the map, Fig. 1, and the isoseismal lines drawn. The data are far too meagre to yield more than rough approximations to the positions of the lines. If a circle of 180 miles radius be drawn with Socorro as its center, it will include all places that felt the shock; it encloses an area of about one hundred thousand square miles, and it seems not improbable that the shock could have been felt over all this region.
It has been impossible to draw the isoseismals higher than V on account of insufficient information, for the region is not thickly settled. The isoseismal III of the shocks of July 12th and 16th probably did not differ much in position from isoseismal IV of November 15th and enclosed an area of about 40,000 square miles.
The smaller shocks usually gave the impression of a single vibration forward and back again; the stronger ones consisted of several vibrations, and the very strong ones apparently had vibrations in different directions, as is usual with strong earthquakes. Sounds, sometimes sharp, sometimes dull, and sometimes like a distant rumbling, occurred at the time of many of the shocks, though some shocks seem not to have been accompanied by sound.
In seeking the origin of this series of shocks we naturally examine the geology of the region. The Rio Grande flows in a broad flat valley on old river deposits hundreds, and in places perhaps more than a thousand, feet thick. The valley is limited a few miles from the river on both sides, by a series of mountain ranges. The whole region is cut by many faults. Flows of eruptive rock have taken place since the Tertiary Period; the Socorro Mountains, immediately west of Socorro, are eruptive; and very recent flows have occurred near Socorro, near San Marcial and elsewhere. The Magdalena Mountains consist of stratified rock resting on early igneous or metamorphic
The formation of a new fault or the movement on an old one, and volcanic explosions, are the two recognized causes of strong earthquakes. The lack of any definite evidence of volcanic activity, the sudden beginning and long continuance of the shocks, their general character and the considerable distance to which the stronger ones were felt, incline us to refer their origins to breaks or slips of the rocks; and the distribution of the intensity suggests that the slips occurred near Socorro--to the west, northwest or southwest. This suggestion is supported by some further evidence. The overthrown chimneys and gables at Socorro fell to the east and the southeastern corner of the postoffice fell outward. The chimneys and gables had their greatest lengths north and south, which would oppose their falling along that line; the fact that they fell to the east and not to the west indicates an origin in general to the west and not to the east as might be supposed; for in any sudden shock the return movement is apt to be stronger than the first forward movement; and in this case the return movement of the earth would have caused the chimneys to fall away from the origin, which would therefore be to the west. We have an example of this principle when window glass is broken by a very loud noise, such as the firing of cannon. The glass falls outward; the first forward movement of the air wave presses the glass in, and the stronger return movement draws it out and breaks it.
About the middle of July Mr. C. B. Allaire at San Antonio and Mr. J. J. Leeson at Socorro, hung up heavy pendulums to record the movement of future shocks. Mr. Allaire's pendulum marked with a pencil on paper, and Mr. Leeson's with a point in a saucer of flour. Before the end of the month Mr. Allaire had recorded two shocks strong enough to yield some information regarding their character. The first indicated a sudden movement of the earth to the southeast; during the return movement there was added a much smaller vibration in a northeast and southwest direction. The second record was like the first but the movement was east instead of southeast. Mr. Leeson reports that his pendulum indicated movements from the northwest. Dr. Bagg set up a similar pendulum in the School of Mines in 1904 and recorded a shock on the night of March 8th of that year in which the first earth movement was toward the east (see below). Unfortunately this pendulum was not kept in operation. From the little information obtainable of the region southeast of Socorro, the intensity
About three and a half miles southwest of Socorro is a lavacapped hill; a comparatively recent fault has cut through the lava and lowered the eastern portion about one hundred feet relatively to the western. A little further east, near where the Magdalena railroad crosses the arroyo, there are two faults in a sandy mud flow. It is, therefore, clear that earth movements have occurred in this region in very recent geologic time, and are probably still continuing.
These various observations lead to the conclusion that the origin of the shocks was a short distance west, northwest or southwest of Socorro. It is not probable that all the shocks occurred at exactly the same point or necessarily on the same fault, but only within the same limited region. Mr. C. T. Brown, a well known mining engineer of Socorro, examined the mines in the Magdalena and in the Socorro mountains and states that no movement occurred on the faults there; this means either that the movement was more deep-seated than the mines, or that the origin was not in these mountains.
The shocks were not very severe, and on rock foundation would scarcely have reached an intensity of more than VII; the water-soaked alluvium near the Rio Grande intensified the damage, and the lack of foundation to the houses and the poor character of the construction (the majority of the houses were built of adobe without any cementing material) permitted greater damage than would otherwise have occurred; and an intensity and destructive power was ascribed to the shocks which they did not actually have.
It is very unfortunate that there were no seismographs in New Mexico, which might have yielded more definite information about the character of the shocks; the very simple devices used for a short time at Socorro and San Antonio have helped materially in pointing out the place of origin.
Mr. J. J. Leeson, voluntary weather observer at Socorro, has sent me a very complete list of the shocks felt in his town from July 2, 1906 to January 16, 1907, which, as already stated, occurred almost daily. Unfortunately his records after the latter date were destroyed by fire, so that we do not know exactly when the frequent tremors ceased.
Light shocks have been reported at Socorro on June 6th, 16th, 17th, 28th and 29th and on July 7th, 11th and 21st, 1907. That of June 28th was also felt at Magdalena. Several shocks occurred in 1908 and five fairly sharp ones in 1909, but none during the first five months of 1910.
It seems characteristic of this region that earthquakes occur in groups. Dr. Rufus BaggAmerican Geologist, 34, 102, 1904. has given some account of a series of thirty-four shocks which occurred between January 19th and March 8, 1904, and referred them to local `displacements in the Socorro Mountains and its outliers." A long series of shocks is reported to have occurred between 1898 and 1900, but I have been unable to get definite information about it. Strong shocks were reported by Dr. Bagg on April 29, 1868, in April 1869, on July 6, 1886, and in 1897; that of 1869 seems to have been the strongest shock recorded before 1906; none of them seem to have done any material damage.
List of Seismographs in America.
[NOTE.--Anyone who knows of a seismograph in operation or about to be installed anywhere in America, and not mentioned in this list, is requested to report it to the Secretary of the Seismological Society of America, Stanford University, California.]
|College St. Martial||Port-au-Prince|
|Magnetic Obs. Station, U.S.||Haiti||J. Scherer||Pendulum|
|Coast and Geod. Survey||Porto Rico||George Hartnell||2 Bosch-Omori|
|Experimental Station Botanical Gardens||Trinidad Kingston,||J. H. Hart||Milne|
|Jamaica||J. F. Brennan||Milne|
|College of Belen (S. J.)||Havana||Rev. G. L. Gangoili||Vicentini|
|Cienfuegos||Rev. S. Sarasola|
|Observatorio Astronomico||Rio de Janeiro||Dr. H. Morize||Bosch-Omori and Wiechert|
|Observatorio Magnetico||Pilar||W. G. Davis||Milne|
|CHILE(The information regarding the stations in Chile is taken from the statement of the director, M. Montessus de Ballore, given in the Boletin del Servicio Sismolojico de Chile, vol. I, Santiago, 1909.)|
|Seismological Service of Chile - Count Montessus de Ballore, Director||Santiago||Bosch-Omori; Wiechert hor. and vert.; and Stiattesi hor.|
|Second order||Tacna||Wiechert hor., 200 k.|
|Copiapo||Wiechert hor., 200 k.|
|Osorno||Wiechert hor., 200 k.|
|Punta Arenas||Wiechert hor., 200 k.|
The following stations of the third order are furnished with Agemennone seismoscopes:
- Evanjelista Island
- Juan Fernandez Island
- Mocha Island
- Puerto Montt
- Punta Dungeness
- San Fernandez
- San Filipe
The Nomenclature of Seismological Reports.
By J. B. Woodworth
At present there is much diversity among different institutions in regard to the use of symols for designating the phases of seismic waves and the data derived from their measurement. The adjoined scheme, known as the Gottingen nomenclature, has been kindly furnished the writer by Dr. Otto Klotz of the Dominion Astronomical Observatory at Ottawa, in which institution the system has been adopted for its seismological reports.
Character of the Earthquake.
Character of the Earthquake.
- = noticeable.
- = conspicuous.
- = strong.
- = terrae motus domesticus = local earthquake (sensible or felt)
- = terrae motus vicinus = near earthquake (under 1000 km.)
- = terrae motus remotus = distant earthquake (1000 to 5000 km.)
- = terrae motus ultimus = very distant earthquake (over 5000 km.)
- = undae primae = first preliminary tremors.
- = undae secundae = second preliminary tremors.
- = undae longae = long waves in principal portion.
- = undae maximae = greatest motion in principal portion.
- = coda = trailers.
- = finis = end of visible disturbance.
Nature of the Motion
Nature of the Motion
- = impetus = beginning.
- = emersio = appearance.
- = period = twice time of oscillation.
- = amplitude of earth movement, reckoned from zero line.
- = E-W component of A measured in microns (μ)
- = N-S component of A measured in microns (μ)
The accompanying table presents in parallel columns a synopsis of several other schemes which are employed in various publications in this country and abroad.
|P||V1||V1||1||I||T||P1||1st P.T.||First preliminary tremors.|
|S||V2||V2||2||II||C||P2||2d P.T.||Second preliminary tremors.|
|L||B||W1||3||III||R||--||-- P.P.||Long or main waves, principal portion.|
|A||..||..||..||..||..||..||..||Amplitude (see note).|
|C||..||..||..||..||..||..||..||Tail, end portion, trailers.|
|..||..||W2||..||..||..||..||..||First reflected long waves.|
|..||..||W3||..||..||..||..||..||Second reflected long waves.|
|..||..||..||..||P||..||..||..||Period of a phase.|
- From the Gottingen system as given above.
- From the reports of the Strassburg international station.
- Given by Professor Hobbs in "Earthquakes."
- Numerals employed in some German publications.
- In reports from Budapest, Hungary.
- In reports from Russia.
- Jesuit Seismological Service, Rev. F. L. Odenbach, S. J. Director, Cleveland, O.
- In some English and Japanese publications.
Where in the above table no letter is given, some evident abbreviation of the term employed is usually given in reports.
By amplitude is sometimes meant the calculated amplitude of motion of an earth particle; in other reports the simple amplitude of motion as recorded by the stylus on the record is meant; some reports give both, e. g., Budapest.
The Gottingen designations appear to be employed by the greater number of stations; and on the advice of Dr. Klotz they have been adopted for future publications from the Harvard station at Cambridge, Mass.
Temblores, Terremotos, Inundaciones Y Erupciones Volcanicas en Costa Rica 1608-1910. Datos compilados por el Lic. Cleto Gonzalez Viquez. San Jose de Costa Rica, 1910. 8°, illustrated, 200 pages.
(Earthquakes, Floods, and Volcanic Eruptions in Costa Rica, 1608-1910. Data compiled by Licentiate Cleto Gonzalez Viquez, etc.)
This book is a painstaking compilation of all the available information regarding earthquakes and related phenomena in Costa Rica during a period of three hundred years. It includes data collected from ancient documents of all kinds, historical writings, newspapers, and every other available source.
The data are divided naturally into three groups:
First, the early and more or less fragmentary records of destructive earthquakes only, covering the period between 1608 and 1851.
Second, personal observations made without instruments from 1851 to 1887, inclusive.
Third, the subsequent systematic and instrumental observations beginning with the work of Mr. H. Pittier, Director of the Instituto Meterologico Nacional, and the installation of a Ewing duplex pendulum and a Blackburn pendulum in 1888.
Among the many interesting things brought out in this work we note at p. 69 that Mr. Pittier's data for 1889 show the greatest number of earthquakes occurred in the rainy months, that is in May and September. At p. 74 Mr. Pittier concludes that the foci of the Costa Rica earthquakes are in the region north of the central plateau.
Of the shocks in 1889 only seven per cent of all had an intensity as high as V, R.-F. scale. In 1890 one shock reached an intensity of VII, while ninety-seven per cent of all were below IV. The detailed records show a large number of shocks, but, with few exceptions, they are quite feeble. In 1900, for example, 103 shocks were recorded (p. 97), only one of which had an intensity of VII. In 1906 the total was 182, but none of them reached an intensity of IV. In 1909 the number fell to four slight shocks. In 1910 no shocks were recorded
One of the most interesting papers in the volume is that by Senor Anastasio Alfaro, Director of the National Museum at San Jose. It deals with the effects of the earthquake of May 4, 1910,--the one that destroyed Cartago.
It is difficult to resist the temptation to quote extensively from a paper of so much dramatic and scientific interest, but lack of space forbids at present. On the subject of the possible relations of the Costa Rica earthquakes to faults, Senor Alfaro appears to think that the bulk of the evidence gathered in that country favors the volcanic rather than the tectonic theory of their origin.
A general conclusion brought out by the data of the book as a whole is that "the epoch of greatest activity of our (volcano) Irazu was in 1723 and that of Turrialba was in 1864, and in those years there were no earthquakes of even average importance. On the other hand when in 1822, 1841, 1888, and 1910, we had genuine earthquakes, these volcanoes have been inactive."
The publication of this valuable contribution to seismology was made possible by the efforts of Professor J. Fidel Tristan of San Jose, Costa Rica, who not only did everything in his power to get together the data, but raised the necessary funds for its printing. The book contains reproductions of many photographs showing interesting volcanic eruptions, and earthquake damages. Such a work is a great credit to any country, and shows that the people are dealing intelligently with the problems imposed upon them by nature.
J. C. Branner.
Report on the Harvard Seismographic Station. By J. B. Woodworth. Reprint from the Annual Report of the Curator of the Muesum of Comparative Zoology, 1908-09, pp. 28-32.
Second Annual Report of the Harvard Seismographic Station. By J. B. Woodworth. Reprinted from the Annual Report of the Curator of the Museum of Comparative Zoology for 1909-10. Cambridge, Mass., 1910, pp. 27-34.
These two reports from the Harvard seismographic station consist chiefly of formal tables and accompanying notes of the shocks recorded by the two Bosch-Omori seismographs during the years 1908-09-10. The first one reproduces the E.-W. component of the record of the Acapulco shock of July 30, 1909. Among the interesting and valuable data given in the second report is a chart designed by Professor Woodworth, and based upon Laska's rules, to facilitate the work of ascertaining the epicenters of distant earthquakes. This table is available for use at any station. J. C. B.
Observations on the Earthquake in the Upper Mississippi Valley, May 26, 1909. By J. A. Udden. Reprinted from Transactions of the Illinois State Academy of Science, III, 1910.
Professor Udden's paper is an interesting and valuable illustration of a method of study of an earthquake where the only data available are personal observations and newspaper reports, and even when the intensity nowhere exceeds VII R.-F. scale. By bringing together these observations he was able to locate isoseismals over an area eight hundred miles in diameter, lying mostly in the states of Illinois, Iowa, and Wisconsin. The area of the highest intensity (about VII R.-F.), forms a T-shaped belt extending from Bloomington, Illinois, on the south, to Kenosha, Wisconsin, on the northeast, and nearly to Platteville, Wisconsin, on the northwest. Remarks tending to discredit the value of newspaper reports of earthquakes are well met by the author's reply to the effect that such data "must be taken for what they are worth and should be used with common sense discretion." The same earthquake was described by Professor Udden in Popular Science Monthly for August, 1910. J. C. B.
The Seismologic Service of Chile
The first number of the Boletin del Servicio Sismolojico de Chile was published at Santiago de Chile in 1909 under the supervision of Count Montessus de Ballore, the distinguished seismologist, and at present the Director of the Seismological Service of Chile. The first number makes a brochure of two hundred pages, and, to the seismologist, it is full from cover to cover of interesting and instructive matter.
The first article is an object lesson of so much value to the geologists of North America, especially to those of us who live in the
We also reproduce on a small scale, as a frontispiece, an outline map of Chile, to show the distribution of the stations established by the Seismological Service in that country.
We cannot refrain from expressing our personal conviction of the wisdom of Chile's action in establishing a seismologic service, in the choice of a director of the highest reputation as a seismologist, and of the admirable way in which the director has gone about his duties.
J. C. B.
Extract from an article in the Boletin del Servicio Sismolojico de Chile I., by M. Montessus de Ballore, Director of the Seismologic Service of Chile.
The Valparaiso earthquake of August 16, 1906, shook up public opinion in Chile and showed the people at large, as well as the representatives of the government, the absolute necessity of developing in this country the study of seismic phenomena, which are probably its most characteristic natural feature. The importance of popular instruction in regard to methods of construction to withstand earthquakes was also vividly realized, and that is a part of seismology which has been completely ignored up to this time, and from which came a large part of the damage caused by that terrible event. In a word, it was realized that Chile could not do without a seismologic service similar to those established in most earthquake countries.
Don Valentin Letelier, Rector of the University, realizing the duty that rested upon him as head of higher education, proposed to the Council of Public Instruction in its session of November 9, 1906, the establishing of a seismologic service and the appointment of a European seismologist, who, besides making the requisite scientific observations, should be entrusted with giving instruction to students of architecture and engineering in the principles of construction in countries subject to earthquakes. This proposition having been adopted by the Council, the plan was finally enacted as a law, and the present director of the service came to Chile toward the end of September, 1907.
After certain preliminaries the seismologic service was organized by decree of June 9, 1908.... It will be sufficient to say that it was decided to establish one central observatory of the first order in Santiago for the observation of earthquakes, both in this country and at a distance.
Four stations of the second order established at Tacna, Copiapo, Osorno, and Punta Arenas, each provided with a hoirzontal Wiechert pendulum of 200 kilos, will serve for observing local and nearby shocks, while twenty-nine stations of the third order, each provided with an Agamennone seismoscope, will permit observations upon local shocks.
The stations of the second order are established in the preparatory schools, and those of the third order are according to circumstances, in charge of the instructors in the schools or of keepers of light-houses.
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The Central Seismological Station at Santiago will supervise all observations, and its personnel includes the Director, an assistant, and a secretary who will also act as draftsman. The last two have been chosen from the older students of the School of Arts and Sciences at Santiago, so that they can attend to the apparatus with the necessary skill, and will be able to take them apart whenever they require cleaning or repairs.
An annual bulletin is published in the annals of the university. Twice a year the Director addresses to the Rector of the University a general report on the operations of the preceding half-year and on the general progress of the service.
The central observatory has been established in a tunnel in the park of the Santa Lucia mountain, and the work of installation, begun in January 1908, was finished in March 1909.... Meanwhile the Copiapo and Osorno stations were established between September 1908 and February 1909.
But it is not enough to register local or regional earthquakes or distant ones; as we know, observations of heavy shocks or those made without apparatus are just as important as those obtained by means of seismographs. This part of the service has been considered with the care it merits. Immediately after the earthquake and under the pressure of public opinion already alarmed by the frequency and intensity of consecutive shocks, the administrative authorities directed the telegraph operators of the state to report by wire strong earthquake shocks felt in their towns.
These employees are charged with certain meteorologic observations which they telegraph daily to the weather bureau of the Quinta Normal at Santiago, and every month they send in detailed reports. Earthquakes are added to the phenomena on which they are to report. Thus, with the active help of the weather bureau there has already been established and is in working order a service for macroseismic observations.
For many years the Hydrographic Office of the Navy has published a meteorological annual, the observations for which are made by the keepers of light-houses scattered along the coast of Chile from Arica to Punta Dunginess and include observations of earthquake shocks.
It therefore only remained to give further development to this organization, and this was begun by extending it to the station masters of the government railways, which was readily done in March 1909, with the cordial support of Sr. Huet, the Director General. The same will also be done with the principals of the primary schools. Finally, many private individuals have spontaneously offered their services in this connection....
On the 15th of April, 1909, a course in seismology as applied to construction was begun in the University for the benefit of students of architecture and engineering.
The Pan-American Congress held at Santiago December 25, 1908, was utilized to establish official agreements with the delegates of neighboring republics, Argentina, Bolivia and Peru, for the purpose of forming a South-Andean Seismological Association so that in these four countries earthquakes may be observed according to a common plan.
The Seismological Society of America
The California earthquake of April 1906 created an intense interest in the subject of seismology, and as one of the results the scientific men of the western coast, interested in the subject, organized a society; and, wishing to make it of more than local scope, gave it the name of the Seismological Society of America. The Society was incorporated under the laws of the State of California, San Francisco being designated as the principal place of business. A board of twelve directors is elected annually in April and these choose their own officers who are also officers of the Society.
Thus far the Society has been able to do but little to justify the name which it has assumed. All the men concerned in its organization have active duties in other lines, there being no such thing at present as a chair of seismology or a department of seismology in any American university. From the beginning the Directors have considered that the issuing of a publication should be one of the chief functions of the Society, but its membership has been small, its financial resources consequently meager, and the Directors could not see their way clear to assuming the financial burdens of a publication. However, at a meeting of the Board of Directors held December 15, 1910, it was unanimously decided that something in this line must be done, and it was thought that, if a decided effort were made to increase the membership, sufficient income could be obtained to support a quarterly publication. A committee on publication, consisting of J. C. Branner, A. C. Lawson and S. D. Townley, was appointed and as a result of their efforts the first number now appears.
The membership has already been increased by over one hundred, and all members of the Society are earnestly requested to help in still further increasing the membership, in order that the publications may be made of the greatest usefulness.
The dues have been placed low, ($2.00 per year, life membership $25.00), and the Bulletin is to be sent free to all members. Inquiries concerning the Society or its publications and names proposed for membership should be sent to the Secretary, S. D. Townley, Stanford University, Cal.
Reports of Earthquakes
In the study of individual earthquakes, one of the most important things to be determined is the center or origin of the shock. This could be obtained from instrumental records if the country was provided with a complete system of seismographs properly distributed and coordinated. In the absence of such a system we must depend, for the present at least, upon the reports of interested persons feeling the shocks. Members of the Society are therefore urged to make records of all earthquakes felt by them and to send the records to the Secretary. It is not necessary to make an elaborate report. The two main points to be determined in any earthquake are the time of its occurrence and its intensity. The time should be recorded to the nearest minute. (More accurate records of time are of course desirable if they can be obtained). The intensity should be estimated on the Rossi-Forel scale which will be found printed on the last page of each issue of the Bulletin.
If the members of the Society would take the trouble to make these simple observations and send in the records it would help greatly in the study of these phenomena.
Send all communications to the Secretary, S. D. Townley, Stanford University, California.
In our next number we hope to give lists of earthquake records of a large number of American stations for the year 1910.
The American Philosophical Society of Philadelphia has appointed a committee to memoralize congress with a view to establishing at Washington a national earthquake laboratory.
There will be a meeting of the International Association of Seismology on July 18, 1911 at Manchester, England. All interested in the meeting are invited to communicate with Professor Arthur Schuster, F. R. S., Manchester.
Professor Harry Fielding Reid of Johns Hopkins University will give eight lectures on seismology and related subjects at the University of California between March 28 and April 6, 1911. The following topics will be treated in his lectures:
General characteristics of earthquakes. Sudden application of forces necessary to cause them. Elastic forces. Slow earth-movements and the strains and stresses produced. Rock folding and faulting, geologic and seismic. Sudden earth movements and their narrow limits. Influence of the plastic and elastic qualities of rock.
Origin and propagation of earthquake waves. The hodograph. Paths of the waves. Deductions as to the earth's interior. The amount of energy in an earthquake and its distriution over the earth's surface. Geographical distribution of earthquakes. Periodicity. Prediction of earthquakes.
Practical study of earthquakes. Observations in the field. Collection of information. Time and intensity.
Isoseismals. The influence of the foundation. Determination of epicenter, depth and time of occurrence. The examination of a seismogram, and the comparison of seismograms. The theory of seismographs. Building in earthquake regions and the protection from earthquake damage.
Minutes of the Meeting of the Board of Directors of the Seismological Society of America, December 15, 1910.
The meeting was called to order by President Branner at 4 p.m. in Room 1404, Merchants' Exchange Building, San Francisco. Directors Branner, Lawson, Louderback and McAdie were present.
Dr. S. D. Townley was elected secretary pro tem. The minutes of the meeting of the Board held on September 16th were read and approved.
The President appointed the Scientific Committee, to consist as follows: C. Derleth, Jr., A. C. Lawson, J. N. LeConte, G. D. Louderback, F. L. Odenbach and H. F. Reid. The President is ex officio a member of the committee. The finance committee was appointed, to consist of A. G. McAdie, chairman, J. N. LeConte, and the Secretary. The auditing committee was also appointed, to consist of G. D. Louderback, chairman, C. Derleth, Jr., and the Secretary.
The retiring secretary reported that the Society has $274.17 in the general account and $234.50 in the savings account, $225.00 of the latter amount constituting a permanent fund of the dues paid by life members.
Following some remarks by President Branner concerning the policy of the Society, and after some discussion of its financial status, it was decided, by a motion duly seconded and carried, to collect the dues for the fiscal year 1910-11 but not to collect those for 1909-10, no notices having been sent out owing to the illness of the former secretary.
It was moved, seconded and carried that the President and the Secretary be appointed a membership committee to secure additional members.
Professor Lawson brought up the matter of securing funds for the purpose of establishing three lines of monuments across the San Andreas Rift. Upon motion of Professor McAdie, duly seconded and carried, a committee of three consisting of the President, Professor Lawson and the Secretary, was appointed to confer with the Board of Trustees of the California Academy of Sciences in regard to the possibility of obtaining from that body a contribution of $5000.00 for the purpose named.
The matter of starting a publication of the Society was discussed at some length, and it was the opinion of all present that this should be done. The President, the Secretary and Professor Lawson were appointed a committee on publication, upon a motion duly seconded and carried.
Six persons were elected to membership in the Society, as follows: Mr. Joseph D. Grant, San Francisco, Cal.; Professor William Libbey, Princeton, N. J.; Professor V. F. Marsters, Lima, Peru; Mr. H. L. Middleton, Boulder Creek, Cal.; Mr. Robert W. Sayles, Cambridge, Mass.; Mr. D. G. Scofield, San Francisco, Cal.
Mr. H. O. Wood made a few remarks concerning the seismographs recently installed at Berkeley, and Rev. Father Ricard some remarks concerning the mathematical formulae for the reduction of seismograms.
The Board adjourned at 5:20 o'clock.
S. D. TOWNLEY, Secretary pro tem.
Rossi-Forel Scale of Earthquake Intensities
- I. Microseismic shock:
- recorded by a single seismograph or by seismographs of the same model, but not by several seismographs of different kinds; the shock felt by an experienced observer.
- II. Extremely feeble shock:
- recorded by several seismographs of different kinds; felt by a small number of persons at rest.
- III. Very feeble shock:
- felt by several persons at rest; strong enough for the direction or duration to be appreciable.
- IV. Feeble shock:
- felt by persons in motion; disturbances of movable objects, doors, windows; cracking of ceiling.
- V. Shock of moderate intensity:
- felt generally by every one; disturbance, furniture, beds, etc., ringing of swinging bells.
- VI. Fairly strong shock:
- general awakening of those asleep, general ringing of bells; oscillation of chandeliers; stopping of clocks; visible agitation of trees and shrubs; some startled persons leave their dwellings.
- VII. Strong shock:
- overthrow of movable objects; fall of plaster; ringing of church bells; general panic, without damage to buildings.
- VIII. Very strong shock:
- fall of chimneys, cracks in walls of buildings.
- IX. Extremely strong shock:
- partial or total destruction of some buildings.
- X. Shock of extreme intensity:
- great disaster, ruins, disturbance of the strata, fissures in the ground, rock-falls from mountains.
Courtesy of The Bancroft Library, University of California, Berkeley, CA 94720-6000; http://bancroft.berkeley.edu/
Title: Bulletin of the Seismological Society of America: Bulletin of the Seismological Society of America: Vol. 1 No. 1
Date: March 1911
Contributing Institution: The Bancroft Library, University of California, Berkeley, CA 94720-6000; http://bancroft.berkeley.edu/
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