A series of small earthquakes rattled the San Francisco Bay Area in an area that's had a lot of seismic activity in recent months. The most powerful of Monday's quakes was a magnitude 4.2 that struck shortly after 7 a.m. just south of San Ramon, according to the U.S. Geological Survey. At least a dozen other smaller quakes struck in the same area starting around 6:30 a.m. and continuing for more than an hour. There were no immediate reports of damage. Bay Area Rapid Transit said delays could result from trains briefly running at reduced speeds during track safety inspections. Shaking was felt more than 30 miles away in San Francisco.

An earthquake with a magnitude of 2.9 struck two miles east-southeast of San Ramon about 8:10 p.m. Saturday, the U.S. Geological Survey said.

A magnitude 3.5 earthquake struck about 4 miles south/southwest of the city of Hollister Sunday afternoon.