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Published October 1978 | Published
Journal Article Open

The source mechanism of the August 7, 1966 El Golfo earthquake


The El Golfo earthquake of August 7, 1966 (m_b = 6.3, M_S = 6.3) occurred near the mouth of the Colorado River at the northern end of the Gulf of California. Synthetic seismograms for this event were computed for both the body waves and the surface waves to determine the source parameters of the earthquake. The body-wave model indicated the source was a right lateral, strike-slip source with a depth of 10 km and a far-field time function 4 sec in duration. The body-wave moment was computed to be 5.0 × 10^(25) dyne-cm. The surface-wave radiation pattern was found to be consistent with that of the body waves with a surface-wave moment of 6.5 × 10^(25) dyne-cm. The agreement of the two different moments indicates that the earthquake had a simple source about 4 sec long. A comparison of this earthquake source with the Borrego Mountain and Truckee events demonstrates that all three of these earthquakes behaved as high stress-drop events. El Golfo was shown to be different from the low stress-drop, plate-boundary events which were located on the Gibbs fracture zone in 1967 and 1974.

Additional Information

Copyright © 1978, by the Seismological Society of America. Manuscript received September 13, 1977. The authors wish to thank Don Helmberger for his assistance throughout the course of this study and Hiroo Kanamori for reviewing the manuscript. This study was supported by National Science Foundation Grants EAR76-06619 and EAR76-14262.

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August 19, 2023
October 17, 2023