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Bulletin of the Seismological Society of America

The Earthquake in The Santa Cruz Mountains, California,
November 8, 1914.

By Carl H. Beal

About 6:30 p.m. on the eighth of November a short, and in some places rather severe, earthquake was felt generally throughout the Coast Ranges of California from Santa Rosa in Sonoma county south-east to Soledad in Monterey county, and as far east as the San Joaquin valley. An intensity of III, Rossi-Forel scale, was estimated in the San Joaquin valley and Santa Rosa, III at Soledad, and II at Fairmead in the San Joaquin valley. Correspondents report that it was not felt as far north as Ukiah, or as far south as San Luis Obsipo.

The area affected was not large, and in order to try out the plan of locating the epicenters of our California earthquakes from personal observations, it seemed worthwhile to gather on the ground such information in regard to intensity as could be had of people who felt the shock. Only about twenty observations and notes were sent in to the Seismological Society of America, the small number probably being due to the fact that the area of highest intensity is in a thinly populated part of the Santa Cruz mountains. About half of the data obtained in this way were furnish by the Spring Valley Water Company of San Francisco. The writer therefore spent four days in the field, and gathered from the people themselves most of the information contained in this brief account. Some information was also obtained by writing directly to acquaintances.

It was evident almost from the first that the intensity was higher in Santa Clara county than it was in San Francisco. A report from Dr. Horace Davis in San Francisco suggests an intensity of about III, while President Branner and Dr. Townley estimated that the shock at Stanford University had an intensity of from IV to VI, Rossi-Forel scale.

An interesting and valuable contribution to the subject was obtained from the experience of a young lady on the campus at Stanford University who was conversing with another lady in San Francisco at the time of the shock. The lady at Stanford felt the disturbance and remarked that she would have to hang up the receiver on account of the earthquake; the lady at the San Francisco end of the line said that no shock had been felt there, and immediately exclaimed. "Here it is now!" Evidently, the wave had passed from the direction of Stanford University toward San Francisco.

The work in the field consisted of the gathering of notes from observers. Many persons were consulted at Stanford University and in the towns of Palo Alto, Mountain View, Santa Clara, and San Jose, and trips were then made to Alviso, Saratoga, Los Gatos, Wrights, Laurel, Glenwood, Skyland, Soquel, Aptos, Watsonville, Gilroy, Morgan Hill, and Coyote. At Watsonville and Gilroy the intensity was estimated at IV, Rossi-Forel scale, but as San Jose was approached the intensity seemed to rise, and in the town of Los Gatos it was evidently much higher than in the city of San Jose.

At Los Gatos the observations of Mr. Snyder, member of the Seismological Society of America, were obtained, and the accompanying record of his seismograph was kindly furnished by him.

Fig. 1. Seismographic Record (enlarged four times). Los Gatos, Cal.,
Nov. 8, 1914. By Irving H. Snyder.

Mr. Synder makes the following comments on the record:

"The seismograph gives some idea of the actual horizontal motion of the earth during the shock, except that the machine enlarges the record to four times that of the real movement. There was also considerable vertical motion, of which no record was made. The maximum motion in a north to south direction was a little less than half an inch, and occurred very close to the beginning of the shock.

This is shown on the right in the record, where the long line extends straight downward to the lowest point. Two small loops, seen near the upper portion of this line, mark the actual beginning of the shock. The upper part of the record shows the movement as the vibrations diminished to zero."

In the town of Los Gatos considerable damage was done, though in no case was it serious. At least six chimneys and two or three window panes were cracked. Small amounts of plaster fell in three houses, six clocks were stopped in the town, and chinaware and bric- a-brac were thrown down. A few showcases in the stores were broken by bottles and canned goods falling from the shelves.

In the Santa Cruz mountains, six or seven miles south of Los Gatos the shock was more severe, but did less damage, probably because of the scarcity of houses. At Laurel, where the intensity seems to have been biggest, two chimneys were broken off and a number of articles fell from the shelves in the grocery store. A number of clocks were stopped, and at one place it was observed that the kerosene in one lamp was violently agitated while that in another twelve feet away had not a ripple on the surface. A similar occurrence was noted four miles northwest at Mr. Van Lone's place, where a small commode was overturned and milk in pans a few feet distant was undisturbed. One mile north of Laurel near the fault line (see Fig. 2) the plaster was badly cracked, and large quantities of it were shaken to the floor. At Terrace Grove a fireplace made of large rounded stones was badly cracked, and one man was thrown to the ground.

The seismograph at Santa Clara University recorded the earthquake shock at 6:31:09 p.m. At Lick Observatory, Mt. Hamilton, it is reported to have begun at about 6:31 p.m., and the actual duration as recorded by the seismograph was 4 minutes 35.2 seconds.

Almost half of the people consulted in regard to the earthquake claim to have heard a low rumble not unlike that of distant thunder, and three or four people within the area of the highest intensity describe the noise as a loud roar. The remainder of the observers report that no noise was heard. At San Francisco, Berkeley, Millbrae, Niles and Palo Alto the noise was reported to have been a low-toned rumble. and at Los Gatos, New Almaden, Coyote and Palo Alto observers state that the noise preceded the earthquake by one or two seconds and continued throughout the duration of the shock.

The earthquake was described by some as a sharp circular jerk preceded by a slight tremor, and by others as a prolonged jolt with two, and perhaps three, distinct maxima of intensity, with the motion of the last at right angles to that of the first. At Mt. Hamilton the earthquake began with a feeble tremor for three or four seconds, suddenly turning into a strong jolt, and gradually diminishing for one or more minutes.

The epicenter of the disturbance was near the small town of Laurel, close to the crest of the Santa Cruz range, and about seven miles south and one mile east of Los Gatos. About the epicenter the intensity was as high as VIII Rossi-Forel scale. The town of Laurel is one mile southwest of the San Andreas-Stevens Creek fault, along which the movement occurred at the time of the earthquake of April 18, 1906. Though no surface evidence was found of movement on this fault line on November 8th, it seems probable that some deep-seated movement on or close to the fault caused the recent shock. This belief is further strengthened by the fact that at the Montezuma School, about four miles northwest of Laurel and approximately on the fault line, two water pipes were broken.

The accompanying map shows most of the district over which the earthquake was felt, and the isoseismals by the Rossi-Forel scale are estimated from the data collected in the field.

Stanford University,
November 28, 1914.

Fig. 2

See San Francisco History Index for more about earthquakes.