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San Francisco Earthquakes


SAN FRANCISCO EARTHQUAKES. The city of San Francisco, California, rests on part of the San Andreas fault and endures hundreds of minor seismic tremors every year. One of the largest tremors occurred at 5:12 a.m. on 18 April 1906, when an earthquake measuring between 7.8 and 8.0 on the Richter scale ruptured the northernmost 430 kilometers of the San Andreas fault. San Francisco experienced unparalleled damage. Hit by falling masonry and buried beneath debris, at least 700

people died. Modern estimates suggest a final death toll in excess of 3,000. Losing its water supply from San Andreas Lake due to a broken pipeline, San Francisco was wracked by uncontrollable fires for four days. Looters pillaged stores and houses. The combination of violent shock-waves and multiple fires destroyed approximately 28,000 buildings and left 250,000 residents homeless. The 1906 earthquake resulted in a substantial rebuilding of the city and, due to its severity, became a lasting source of study into plate tectonics and seismic motion.

At 5:04 p.m. on 17 October 1989, San Francisco suffered another large earthquake. Geologists named it the Loma Prieta earthquake after its epicenter close to Mount Loma Prieta, sixty miles southeast of the city. The earthquake measured 7.1 on the Richter scale. Approximately thirty times less powerful than its 1906 precursor, the earthquake still tested the preparedness of northern Californians for a sizable seismic event. Famous for interrupting a live, televised World Series baseball game at Candlestick Park in San Francisco, the Loma Prieta earthquake caused substantial damage to communities in and around the city. Buildings in Santa Cruz and Watsonville, close to the epicenter, collapsed during a succession of wrenching shockwaves. In Oakland, across the bay from San Francisco, the Cypress Street section of Interstate 880, a two-tier freeway, collapsed. Seismic tremors damaged 18,000 houses and rendered 12,000 residents temporarily homeless. Officials later calculated the total cost of damage at $6 billion; sixty-three people died.


Hansen, Gladys, and Emmet Condon. Denial of Disaster: The Untold Story and Photographs of the San Francisco Earthquake and Fire of 1906. San Francisco: Cameron, 1989.

McPhee, John. Assembling California. New York: Farrar, Straus, 1993.

Plafker, George, and John P. Galloway, eds. Lessons Learned from the Loma Prieta, California, Earthquake of October 17, 1989. United States Geological Survey Circular 1045. Washington, D.C.: Department of the Interior, 1989.


See alsoDisasters ; Earthquakes .

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