There was a 3.4-magnitude earthquake centered near Alamo at 7:44 a.m. on Tuesday.
The USGS rated this tremor, which was about a mile northwest of Alamo, as "minor."
A viewer in Walnut Creek said it knocked framed pictures off of shelves.
There were also reports that the quake was felt in Concord and Berkeley.
There were no reports of major damage.