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by R.W. Sherburne, D.L Parke, M.J. Huang and A.F. Shakal
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Introduction
During the months of July, August, and September in 1986, a series of
earthquakes occurred in the rural Chalfant Valley, located about 18 km (11
miles) northeast of Bishop. This series of shocks was reported to have caused
about $2.7 million in damages (The Sacramento Bee, September 11, 1986).
Approximately 50 mobile homes in the Chalfant area were knocked from their
foundations during these earthquakes. In addition, several non-mobile homes
were heavily damaged, and one frame house nearly collapsed (The Sacramento
Union, July 22, 1986).
Field geologists identified approximately 11.5 km (7 miles) of surface
faulting on several traces of the White Mountain fault zone (Kahle et al.,
1986). A maximum of 5 cm of right lateral slip was observed. East-west
extension across cracks which occurred in conjunction with known fault
segments was also observed.
Many earthquakes of this series were recorded at strong-motion stations
of the California Strong Motion Instrumentation Program (CSMIP), and the U.S.
Geological Survey (USGS). Records recovered from USGS stations during the
July 21 mainshock are given in Maley et al. (1986). This report presents
copies of 36 accelerograms recorded at CSMIP stations during the four largest
shocks: 21 July 1986, ML 6.4 (mainshock); 20 July 1986, ML 5.9 (foreshock);
21 July 1986, ML 5.6 (called Aftershock #1 in this report); 31 July 1986, ML
5.8 (Aftershock #2). The location and origin times of these four earthquakes
are given in Table 1. Table 1 also lists the number of records recovered for
each earthquake by station type.
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