The 1971 event was the first in a series ( 1987 Whittier Narrows , 1991 Sierra Madre , 1994 Northridge ) of damaging earthquakes which have occurred on reverse faults in the Los Angeles area . The events triggered discussions concerning the largest magnitude earthquake that could be generated by one of the faults , especially in the Transverse Ranges , but the focal point of earthquake hazard assessments in California are often the San Andreas Fault and other associated dextral faults . Although there is a lack of paleoseismic data on reverse faults in the Los Angeles area , a trench excavation at a site on the Sierra Madre-Cucamonga Fault revealed that two large historic earthquakes occurred in the last 15,000 years
1994 Northridge
1994 Northridge earthquake
Sierra Madre Fault Zone