A 6.0-magnitude earthquake has rocked California's scenic Napa Valley wine country, the strongest to hit the region in a quarter of a century, seriously injuring three and jolting thousands from their sleep.
No deaths were reported but a child was in critical condition after being crushed by a fireplace and authorities said more than 120 people sought minor medical care.
California's governor declared a state of emergency in the wake of the 3:20am quake, which ignited fires, burst water mains, caused gas leaks and cracked roads.
The US Geological Service said the tremor was the most powerful to hit the San Francisco Bay area since the 1989 6.9 magnitude Loma Prieta earthquake.
Many Napa residents and the surrounding area were roused from sleep when the ground started shaking, sparking panic.
Napa city officials said three people suffered serious injuries, including a child who had to be airlifted to a hospital for neurological care.
The Queen of the Valley Medical Centre meanwhile treated 120 patients for minor injuries such as cuts and bruises.
Napa officials scrambled to flag 16 buildings, including a senior centre, as too damaged for occupancy, as portions of the city's downtown were cordoned off with yellow tape.
Fire destroyed four mobile homes and damaged two others at a trailer park in the area, while crews extinguished blazes in two other residential neighbourhoods.
As inspectors went from building to building to check safety and risk of further collapse, Napa city officials said they had received more than 100 phone calls from people reporting gas leaks.
However, city public works director Jack LaRochelle said "the big thing we're looking at from a public-works and infrastructure standpoint is the water-main system".
The Napa city official said 60 water-main breaks occurred following the quake, which struck near American Canyon some 64km northeast of San Francisco, according to USGS.
LaRochelle said that 20 of the breaks had been isolated and shut off and that five teams were working in 12-hour shifts to restore water to areas where it didn't exist or had minimal pressure.
He added that Napa's roads were in good shape with only a handful of "buckling streets, but nothing that's really serious enough to cause us to close a road. Our bridges are in pretty good shape".
Power remained knocked out to around 20,000 customers in the area, home to California's most celebrated wine-producing regions, according to the Pacific Gas and Electric Company. Brown said 69,000 people had lost power.
