A magnitude 6.0 earthquake in Napa Valley has injured dozens of people, damaged historic buildings and cut power to tens of thousands of homes.
The quake struck at 3.20am local time about 10km from Napa city and was measured at 11.2km deep by Geological Survey.
It was widely felt in across northern California and was the largest to hit the San Francisco Bay Area in the 25 years since the devastating magnitude 6.9 Loma Prieta quake in 1989.
It collapsed part of the Bay Bridge roadway and killed more than 60 people, most when an Oakland freeway fell. The most serious casualties in the latest quake are two adults and a child, who are reported to be critically injured.
Water mains and gas lines have been ruptured, power lines brought down, fires ignited and roads blocked. Governor Jerry Brown declared a state of emergency for southern Napa County, directing state agencies to respond with equipment and personnel.
Dazed residents too fearful of aftershocks to go back to bed wandered at dawn through Napa’s historic downtown, where the quake had shorn a 10ft chunk of bricks and concrete from the corner of an old county courthouse.
Boulder-sized pieces of rubble littered the lawn and street in front of the building and the hole left behind allowed a view of the offices inside.
Napa fire operations chief John Callanan says the city has exhausted its resources trying to extinguish six fires, some in places with broken water mains; transporting injured residents; searching homes for anyone who might be trapped; and answering calls about gas leaks and downed power lines.
Two of the fires happened at mobile home parks, including one where four homes were destroyed and two others damaged, he says.
The earthquake sent at least 87 people to Queen of the Valley Medical Centre in Napa, where officials set up a triage tent to handle the influx. Most patients had cuts, bumps and bruises.
Napa city manager Mike Parness says 15-16 buildings are no longer inhabitable and thereis only limited access to numerous other structures, mostly ones with broken windows.
Pacific Gas and Electric says close to 30,000 people lost power right after the quake hit but the number still affected is just under 19,000, most of them in Napa.