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The Northridge Earthquake of 1/17/94, Part I (20 Images)

Set 1: Community of Northridge

This presentation is based on a 35mm slide set with the same title published by the U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, Boulder, Colorado 80303, USA (Product No. 647-A11-018

The Earthquake

At 4:31 A.M. (local time) on Monday, January 17, 1994, a magnitude 6.8 earthquake woke nearly everyone in southern California. The earthquake epicenter was beneath the San Fernando Valley, 20 miles (32 km) west-northwest of downtown Los Angeles, near the community of Northridge (34° 13' N, 118°32'W).

The main shock occurred on a shallowly-dipping, previously unknown thrust fault. The rupture started at a depth of about 12 miles (19 km) and, during the course of the main shock, traveled upward and northward, spreading both eastward and westward. The focal mechanism of the main shock from both first motions and teleseisms shows a N 60° W striking and 35° to 45° south dipping plane. Rock on the south side of the fault surged upward and over the rock on the north side. As a result of the quake, the Earth's crust south of the San Fernando Valley moved slightly closer to the Earth's crust north of the valley, and the mountains just north of the valley are slightly higher.

The Damage

Damage was most extensive in the San Fernando Valley, the Simi Valley, and in the northern part of the Los Angeles Basin. After the earthquake, a total of 24,000 dwellings were vacated. The death toll from the quake was 57. The total cost of the earthquake was estimated to be at least $10 billion. The Northridge earthquake is significant since it was the most expensive earthquake and one of the most expensive natural disasters in United States history, yet it occurred on a previously unknown fault.

Northridge Fashion Mall: The Northridge Fashion Mall was extensively damaged by the earthquake. Bullocks Department Store in the mall collapsed. One parking structure collapsed into a pile about twenty feet high. Other department stores and parking structures were also damaged. Windows were shattered throughout the mall. Severe damage and partial collapses were seen in other, smaller shopping centers near the epicenter.

Northridge Meadows Apartment Complex: Not far from the Northridge Fashion Mall, sixteen people were killed when the 164-unit Northridge Meadows Apartment collapsed. In an area of several square miles, intense damage occurred to apartments built in the 1960s and early 1970s (prior to the latest revisions in the building codes for multi-family housing). Many of these apartment buildings had "soft" first stories.

California State University Campus: Most of the 60 buildings on the campus performed well and there were no injuries nor deaths on the campus. One parking structure collapsed and three buildings were severely damaged and were unrepairable. Fifteen to twenty buildings required structural repairs and retrofitting to meet structural codes. Inside the buildings the contents were severely disturbed.

Freight Train Derailed: A 64-car Southern Pacific freight train carrying hazardous material derailed between the communities of Chatsworth and Northridge. Sulfuric acid was released from one of the sixteen tank cars carrying the substance. Two thousand gallons of diesel fuel spilled from the locomotive.

Northridge Community Center Hospital: At Northridge Community Center, located near the epicenter, patients in wheelchairs were rushed outside. There was no water, no power, and no telephone service. At the same time, the hospital was deluged with requests for treatment from people suffering injuries in the earthquake.