Three people were seriously injured and nearly 90 patients have been treated at one hospital.
The city of Napa said in a statement Sunday that two adults and one child have critical injuries and Queen of the Valley hospital in Napa has treated 87 people. Hospital spokesman Vanessa DeGier says most patients have cuts, bumps, bruises.
Officials say widespread power outages have been reported in Sonoma County.
Jennifer Jones Lee, who lives in the earthquake area, told Fox News the tremor “felt like someone just picked up the house, shook it for a while, then dropped it. It was incredibly violent.”
Arik Housley, who owns two grocery stores in the area, said he was awakened at about 3:30 a.m. by the shaking. “It was very jolting and probably went for 20 seconds . . . it was shaking pretty good,” said Housley, whose brother is Fox News senior correspondent Adam Housley.
Arik Housley said he passed a mobile home park where multiple fires could be seen as he drove to one of his stores to assess the damage. Housley said the shelving in his store had moved 2 feet to 3 feet from the wall, and much of his inventory had fallen to the floor, including $200 bottles of wine. Many merchants in the area forgo earthquake insurance because it’s too expensive, he said. A quake about 14 years ago resulted in about $30,000 in damage, he told Fox News, and speculated the current damage would be in excess of $100,000.
"There's collapses, fires," said Napa Fire Capt. Doug Bridewell, standing in front of large pieces of masonry that broke loose from a turn-of-the-century office building where a fire had just been extinguished. "That's the worst shaking I've ever been in."
Bridewell, who said he had to climb over fallen furniture in his own home to check on his family before reporting to duty, said he was starting to see more reports of injuries.
The tremor set off car alarms and had residents of neighboring Sonoma County running out of their houses in the middle of night.
The USGS says the depth of the earthquake was just less than 7 miles, and numerous small aftershocks have occurred in the Napa wine country.
A member of Napa County dispatch tells The Associated Press that there has been one report of structural damage, but additional details were not available.
“There’s fires, debris all over the streets, everywhere,” Napa resident Karen Hunt told “Fox & Friends.”
Hunt said her husband, who is an engineer, shut off the gas line to their home to guard against explosions, then went to neighbors’ homes to do the same.
“Right now we’re just waiting for the aftershocks,” she said. She said she had not felt any, but reportedly there has been two, one at magnitude 2.5.
Hunt has said she has felt other earthquakes, but “this is way on top of anything I’ve ever felt.”
Hunt, who has lived in Napa since 1996, owns a winery. She said she heard from her partner that her 2011 and 2012 vintages had been destroyed.
“That’s pretty devastating if that’s the case,” she said.
Thousands of small earthquakes occur in California each year, providing scientists with clear indications of places where faults cut the Earth's crust. There were 4,895 earthquakes in California between 1974 and 2003 with a magnitude of 3.5 or greater (about 163 per year).