An immediate field survey of the San Fernando, Los Angeles, earthquake, February 9, 1971
The San Fernando earthquake occurred in the San Gabriel Mountains, about 25 miles to the north of central Los Angeles. Its magnitude, about 6 1/2, was not exceptionally large, and such earthquakes are not uncommon in California. Not since the Long Beach earthquake of 1933 (magnitude 6.3), however, has a significant shock occurred near a densely built-up area. The greatest damage appears to be associated with a zone of overthrusting, where the San Gabriel Mountains meet the San Fernando Valley to the south of the epicentre. In some places this overthrusting caused conspicuous ground deformation through built-up areas of San Fernando and Sylmar.
Domestic wooden-frame houses in general withstood the earthquake well, but large hospital buildings at the Olive View Medical Center and Veterans’ Administration Hospital at Sylmar failed badly. Conspicuous damage was also caused to freeway overpasses, the Sylmar Converter Station, and to the Van Norman Reservoir complex. Total damage is estimated as high as U.S. $1,000,000,000. Ground accelerations of about 1g were recorded in the abutment of the Pacoima Dam, to the north of San Fernando.
Copyright (c) 1971 R. D. Adams
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