Northridge earthquake of 1994 | Cause, Magnitude, & Facts (2024)

Northridge earthquake of 1994, earthquake that struck the densely populated San Fernando Valley in southern California, U.S., on January 17, 1994. The third major earthquake to occur in the state in 23 years (after the 1971 San Fernando Valley and 1989 San Francisco–Oakland earthquakes), the Northridge earthquake was the state’s most destructive one since the San Francisco earthquake of 1906 and the costliest one in U.S. history.

The earthquake occurred just after 4:30 am local time along a previously undiscovered blind thrust fault in the San Fernando Valley. Its epicentre was in Reseda, a suburb located about 23 miles (37 km) west-northwest of downtown Los Angeles. The major shock lasted 10–20 seconds and registered a magnitude of 6.7.

Fatality estimates range from just under 60 to more than 70 people killed, with most studies placing the number at around 60. The timing of the earthquake (early morning during a federal holiday) is thought to have prevented a higher death toll, as most residents were in their beds, rather than on failed freeways or in other collapsed structures (such as office buildings or parking lots). Most of the casualties occurred in wood-frame apartment buildings, popular in the San Fernando Valley, and particularly in those with weak first floors or lower-level parking garages.

Property damage was severe and widespread; although the worst damage was sustained by communities in the western and northern San Fernando Valley, other areas of Los Angeles county were affected, as were parts of Ventura, Orange, and San Bernardino counties. The percentage of buildings completely destroyed was relatively low in light of the strength of the ground motions. Nevertheless, tens of thousands of buildings were damaged, with many “red-tagged” as unsafe to enter and many more restricted to limited entry (“yellow-tagged”). A significant portion of the transportation system around Los Angeles was shut down, as sections of major freeways (including the Santa Monica Freeway and the Golden State Freeway) collapsed and numerous bridges sustained heavy damage. Fires that broke out in the San Fernando Valley and in Venice and Malibu caused additional harm.

The extent of the property damage in an area so well-prepared for earthquakes was staggering. Accordingly, a number of legislative changes were made in the aftermath of the Northridge earthquake. Most significantly, the state created the California Earthquake Authority, a publicly managed but privately funded organization offering basic residential earthquake insurance.