Moderate M 5.2 earthquake shakes the SF Bay Area

Seismo-Watch

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Monday, May 13, 2002

An earthquake registering M 5.2 occurred this evening in the south San Francisco Bay Area about 3 miles southwest of Gilroy, California. Early reports indicate it was widely felt in the region, causing minor damage but there have been no reports injuries at this time.

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According to the Northern California Seismic Network (NCSN) the earthquake measured M 5.2 occurred at 05:00:29 GMT, May 14, or 10:00 p.m. PDT , May 15, about nine miles northwest of San Juan Bautista and three miles southwest of Gilroy in the upper reaches of Pots Creek valley, just northwest of the hairpin bend in Castro Valley Road. See a Topozone topographic map or a MapQuest street map. This is the southern extent of the Santa Cruz Mountains.

The focal depth was at 7.9 km, a typical depth for earthquakes in this location. Preliminary analysis by UC Berkeley suggested a Moment magnitude (Mw) 4.9 and their fault plane solution indicated strike-slip motion along a northwest trending plane. See the UC Berkeley solution.

The earthquake was center along the Castro splay of the Sargent fault zone, which has shown elevated activity during the past three weeks, including two quakes registering M 3.0 on April 29 and a M 3.1 on May 2. Minor tremors have occurred on and off since then. See the Seismo-Watch Central California Earthquake Report.

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