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Effects Of Sylmar Earthquake On San Fernando Valley

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One of the most significant earthquakes to hit the San Fernando Valley in the past was the 1971 San Fernando/ Sylmar earthquake. On February 9, 1971 at about 6 o’clock the cities of San Fernando and Sylmar experienced an earthquake that ruptured along the Sierra Madre Fault Zone (Oakeshott, Gordon B). The epicenter of this earthquake was reported to be in the San Gabriel Valley Mountains above the valley. The citizens of both cities felt tremendous shaking. The magnitude of the earthquake was measured as a 6.6 on the Richter scale and the shaking had the intensity of a level 11 (extreme) on the Modified Mercalli system (U.S. Geological Survey). The shaking of this 6.6 magnitude earthquake lasted about 12 seconds with a very strong ground motion. The source of this faulting was located about five miles to the north of the San Fernando valley. The surface faulting of this earthquake was reported to be seen along the surface of the San Fernando fault zone from a point south of Sylmar, the faulting stretched 6 miles more as far as east to the little Tujunga Canyon, also more surface faulting was reported more east as well. In total the maximum surface rupture was 12 miles and the amount of slip was about 6 feet (U.S. Geological Survey). The type of fault scientist label this earthquake to be was an oblique-slip or also known as a thrust. The depth of this earthquake was 13km (8.1 mi) and the peak acceleration was when it reached the Pacoima dam having the speed of 1.25g (U.S.

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