An earthquake with a preliminary magnitude of 4.2, later revised at 4.0, shook the East Bay Monday evening and was felt as a brief shake in San Francisco.

The earthquake struck at 7:46 pm, and the epicenter was 5 kilometers west-northwest of Dublin, California.

There have been no reports of damage, and just the usual Xitter activity following the shaking.

The early ShakeMap below, from the USGS, only shows reports of shaking on the Peninsula, but the earthquake definitely shook San Francisco as well!

Map via USGS

The last significant earthquake in the Bay Area, a 3.7M, was also in the Bay Area, slightly north of this one, and it happened on January 12. It occurred on the relatively inactive Concord-Green Valley Fault, east of the Hayward Fault.