Earthquakes in the Walker Pass Region, California, and their Relation to the Tectonics of the Southern Sierra Nevada

Citation

Gardner, John Kelsey (1964) Earthquakes in the Walker Pass Region, California, and their Relation to the Tectonics of the Southern Sierra Nevada. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/R906-T104. https://resolver.caltech.edu/CaltechETD:etd-10152002-100918

Abstract

The locations and depths of earthquakes occurring in the Walker Pass Region, California, and the surrounding area have been examined for the period from January, 1934, to December, 1963. Whenever possible, least-square computer locations programs have been used to check or revise the previously determined epicenters and origin times. In most cases, epicenters determined by machine methods are within ten kilometers of those previously assigned. Accurate depths, whenever they could be calculated, were always found to be less than fifteen kilometers and usually less than ten kilometers.

The sequence of earthquakes occurring in the Walker Pass region in March, 1946, has been carefully examined. While no major shifts in epicenters were found, the depth of the main shock of this series has been revised from twenty-one kilometers to less than ten kilometers. This revision cast doubt on the assertion that the earthquake originated on the Sierra Front Fault and made it likely that the earthquake occurred on one of the northwest-southeast trending faults in the interior of the Sierra mass.

Finally, the general distribution of earthquakes furnishes no evidence for the existence of a continuous deep-lying structure traversing the southern part of the Sierra Nevada. While the possibility of the existence of such a structure has not been excluded, practically all of the evidence upon which such a speculation might be based has been removed. Any relation between activity in this region and the activity in the nearby White Wolf Fault region must instead be explained by means of a mutual transfer of strain between systems of different trend and character.

The computer programs used for the location of the earthquakes reported in this study are discussed in Appendices A and B.

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