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Published June 1968 | Published
Journal Article Open

The Borrego Mountain, California, earthquake of 9 April 1968: A preliminary report


The largest earthquake to hit California in more than 15 years occurred at 02:28:58.9 GCT on 9 April 1968 near Borrego Mountain, on the western edge of the Imperial Valley. The Seismological Laboratory at Pasadena has tentatively assigned the shock a magnitude of 6.5, an epicentral location of 33 ° 08.8' N, 116 ° 07.5' W, and a focal depth of 20 km. The earthquake was felt throughout most of southern California and adjacent areas, but the absence of severe damage and casualties was in large part due to the relatively undeveloped nature of the epicentral region. Indeed, it would have been difficult to pick a location in the southernmost part of the State more remote from centers of population.

Additional Information

Copyright © 1968, by the Seismological Society of America. Manuscript received April 29, 1968. Participation in this study by the California Institute of Technology was supported by National Science Foundation Grant GA-1087. A joint contribution of the California Institute of Technology, Division of Geological Sciences (Contribution No. 1532) and the National Center for Earthquake Research, U.S. Geological Survey.

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