SAN RAMON, Calif. — More than two dozen minor earthquakes shook the suburbs east of San Francisco on Sunday, but no injuries or damage were reported.
The quakes, in what seismologists call a "swarm," began about 8:15 a.m. and continued throughout the day, according to the U.S. Geological Survey.
Centered near the upscale suburbs of Dublin and San Ramon, about 25 miles east of San Francisco, the swarm included at least 28 quakes by nightfall.
"These are the faults that we're most concerned about for big earthquakes in the region," said David Schwartz, a seismologist for the Geological Survey.
The strongest quake struck at mid-morning, and was felt in Berkeley, just across the bay from San Francisco, about 15 miles from the epicenter.
The quakes occurred near an area close to where a similar cluster shook the region late last year.
But Sunday's shakers were probably caused by a different section of the Calaveras fault system, according to Schwartz.
The quakes are the largest to occur this close to the Calaveras fault in the 40 years that the Geological Survey has been monitoring it, Schwartz said.