The 1971 San Fernando earthquake (also known as the Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in southern California. The unanticipated thrust earthquake had a moment magnitude of 6.5 or 6.7 (as determined by several independent institutions) and had a maximum Mercalli intensity of XI (Extreme). The event was one in a series that affected the Los Angeles area in the late 20th century, and a study of the Sierra Madre Fault during that time indicated that more substantial thrust earthquakes had occurred near the Transverse Ranges in the past. Damage was locally severe in the northern San Fernando Valley, and surface faulting was extensive to the south of the epicenter in the mountains, as well as urban settings along city streets and neighborhoods.