A magnitude 3.6 earthquake was reported about 5:27 p.m. Satuday, originating a mile and a quarter north-northwest of Crockett, in unincorporated Contra Costa County, the U.S. Geological Survey reported.
The USGS indicates that point would be just across the Carquinez Strait from Crockett, in the Carquinez Heights area of southernmost Vallejo.
"It was very fast, less than five seconds, like the earth shifted but we all almost got knocked off our seats for a second," said Candice Garcia from Crockett.
Early social media reports indicate the temblor was felt over an area ranging from Concord and Oakland to American Canyon. There were no reports of damages early Staurday evening.