The quake struck at 7:43 a.m. and had a depth of 8.3 miles, USGS officials said.
The quake was centered in Round Valley Regional Park, about 7 miles south-southwest of Brentwood and 7 miles west-southwest of Byron, according to the USGS.
2.8 earthquake strikes east of Mount Diablo
UNINCORPORATED CONTRA COSTA COUNTY
