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OSMS 78-7.1

by R.D. McJunkin

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A moderate magnitude earthquake (ML = 5.7; Berkeley Seismographic Station) occurred approximately 30 km northwest of Bishop, California at 16:42:47.3 (GMT) on 4 October 1978. The earthquake had a focal depth of 4.8 km and was located at latitude 37.518°N and longitude 118.705°W.

The Bishop area is moderately instrumented by 11 accelerograph sites within 100 km of the epicenter (Figure 1; Table 1). All instruments within the 100 km epicentral radius are owned and operated by the Office of Strong Motion Studies (OSMS), California Division of Mines and Geology (CDMG). Five of the eleven OSMS accelerograph stations were triggered (Figure 2) and produced records of the Bishop earthquake.

Three accelerograph sites beyond the 100 km epicentral radius were triggered by the 4 October 1978 earthquake. Two sites at the Pine Flat and Buchanan Dams (Ed Etheredge, 1978, person. commun.) are instrumented by the USGS; the third site, on the Fresno State University campus, is instrumented by OSMS. Records from these three distant stations are very weak and were determined to not be significant in comparison with data obtained from sites closer to the epicenter. For this reason, data from the three distant sites are excluded from this report.