First Fault Within San Francisco Discovered

Despite its history of destructive earthquakes, geologists have only just now found what appears to be a fault within San Francisco’s borders.

Scientists say the fault is a relatively benign extension of the Serra thrust fault. Until now, that fault had been mapped only as far as Daly City, just to San Francisco’s south.

The fault poses nowhere near the threat of the San Andreas fault, which cuts straight through towns to San Francisco’s south, but heads out to sea just south of the city’s border.

New details of the little-known thrust fault were presented Friday by San Francisco State University researchers. The researchers say the buried fault has not rumbled to life recently and was apparently quiet during the 1906 San Francisco and 1989 Loma Prieta quakes.