Strongest quake in rural California since 1940

A rural area of Northern California experienced its strongest earthquake since 1940 on Wednesday morning, causing some injuries but no immediate reports of major damage, officials said.

The epicentre of the quake, with a preliminary magnitude of 5.6, was about 12 kilometres northwest of the agricultural town of Willits, according to the US Geological Survey. It was widely felt, including in the coastal city of Fort Bragg. The initial quake was centered inland about 80 kilometres east of Fort Bragg at 8:10 am PT, and the USGS said it was about 8 kilometres deep.

The area in Mendocino County dotted with small, agricultural towns is 225 kilometres northeast of San Francisco.

Heather Rose, a Mendocino County spokesperson, said that hospitals had reported some injuries but that she had no details on their nature or extent. She said officials plan to meet later Wednesday when more information could be released.

Power outages are affecting more than 6,000 residents of six towns near the epicenter, the Mendocino County Executive Office said in a statement. The office encouraged people to stay off the highways and roads to allow work crews to inspect for damage and make repairs.

Brie Leon and her colleagues had just opened Club Calpella Restaurant when the building started shaking, rattling plates and liquor bottles.

"I had just turned the open sign on and went back into the kitchen, and that's when it happened," she said. "It almost felt like something hit the building."

The restaurant is in Calpella, California, a town about 16 kilometres south of the epicenter and in a region of Mendocino County that has been struck by smaller quakes this year.

This was the biggest earthquake in nearly nine decades in the region, which is not on a major fault, said Lucy Jones, a veteran California seismologist.

"The area is not without earthquakes, but they're usually smaller than this," Jones said. She added that aftershocks are likely, but they'll "probably stay on the low side."

Three other quakes under a 2.7 magnitude struck near the epicenter within an hour.

Leon said the quake knocked frames off the walls and bottles off the shelves in the restaurant and the stockroom next door. She and other servers were cleaning up not long after to welcome customers for breakfast.

"It wasn't a big, big quake, but things went everywhere," she said.