For the second time in less than 24 hours, the ground in and near Martinez shook and startled a host of people, who began posting their experiences on Facebook.
Did you feel the ground move this morning? According to the US Geological Survey, the epicenter was near the same place as last night - between Crockett and Vallejo, at a depth of 5.7 miles.
No damage was reported so far in either incident.
Tell us your experience with the tremor.