9, 1971 (M=6.5)
The San Fernando earthquake of February 9, 1971, ranks as one of the most serious California earthquakes in historical time. The event claimed 58 lives and caused more than half a billion dollars in property damage, including the destruction of two hospitals, a freeway interchange, and the Van Norman Dam. The earthquake ruptured north-dipping, high-angle reverse faults be-neath the southern margin of the San Gabriel Mountains and broke the surface along a discontinuous, 15-km-long zone. Surface displacements averaged about 1 m. Seismograms of the earthquake reveal a steeply dipping deep fault and a more shallowly dipping near-surface fault (Langston, 1978; Heaton, 1982). Numerous publications report on detailed investigations of this event, including the summary report published by the U.S. Geological Survey (1971).