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Earthquake Loma Prieta California 1989

Earthquake Loma Prieta California 1989 The Loma Prieta earthquake was a major earthquake that struck the San Francisco Bay Area of California on October 17, 1989, at 5:04 p.m. local time. Caused by a slip along the San Andreas Fault, the quake lasted 10–15 seconds and measured 6.9 on the moment magnitude scale, or 6.9 on the open-ended Richter Scale. The quake killed 63 people throughout northern California, injured 3,757 and left some 3,000-12,000 people homeless.

The highest number of fatalities, 42, occurred in the City of Oakland because of the failure of the Cypress Street Viaduct on the Nimitz Freeway (Interstate 880), where a double-deck portion of the freeway collapsed, crushing the cars on the lower deck. One 50-foot (15 m) section of the San Francisco – Oakland Bay Bridge also collapsed, leading to the single fatality on the bridge. Three people were killed in the collapse of the Pacific Garden Mall in Santa Cruz, and five people were killed in the collapse of a brick wall on Bluxome Street in San Francisco.

On October 18, 1989, the U.S. Senate Committee on Commerce, Science and Transportation and the U.S. House of Representatives Committee on Science, Space and Technology requested the National Institute of Standards and Technology (NIST) investigate earthquake damage including the elevated section of Interstate 880 and the other bridge structures.  The team traveled to the San Francisco area and carried out its investigation during the period of October 18-26, 1989. 

See the NIST report, "Performance of Structures During the Loma Prieta Earthquake of October 17, 1989," for more information.

 Aerial view of collapsed sections of the Cypress viaduct of Interstate Highway 880. (Photo credit: H.G. Wilshire, U.S. Geological Survey)

Aerial view of collapsed sections of the Cypress viaduct of Interstate Highway 880. (Photo credit: H.G. Wilshire, U.S. Geological Survey.)

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H. S. Lew