San Fernando Earthquake of 9 February 1971: Pattern of Faulting

Mapping of the surface breaks that resulted from the San Fernando earthquake of 9 February 1971 reveals that the pattern of faulting was highly complex; it consisted of a number of segments that produced ground displacements and acceleration throughout the entire northern end of the San Fernando Valley. Instead of occurring on the frontal fault zone, as might have been expected, the faulting occurred on the valley side of the frontal fault system, which separates the crystalline rocks of the San Gabriel Mountains from the Tertiary sediments of the San Fernando Valley. However, the new fault system does, in many cases, follow breaks in slope and subtle escarpments that suggest faulting along these zones in the recent geologic past.