A magnitude 7 earthquake has hit off the northern California coast, prompting an immediate tsunami warning for hundreds of kilometres of the California and Oregon coasts.

Some 4.7 million residents of California and Oregon were under the tsunami warning until it was cancelled, the US National Weather Service said.

The quake, which hit on Thursday (local time) at a shallow depth of 10 kilometres, was centred about 65 kilometres west of the town of Ferndale, a sparsely populated portion of the northern California coast, the US Geological Survey said.

It was the strongest quake to hit the region since a tremor of 7.2 in 2005.

Tens of thousands of people reportedly felt the tremor, reporting signs and chandeliers swaying back and forth. Elsewhere, people reported the water in home pools sloshing around, and sometimes spilling.

Tsunami Warning 1 for areas of OR & N. CA: See https://t.co/npoUHxX900 for alert areas. M7.3 045mi SW Eureka, California 1044PST Dec 5 pic.twitter.com/NFCbU5EaKa

— NWS Tsunami Alerts (@NWS_NTWC) December 5, 2024

There were no immediate reports of serious injuries, but the tremor did cause some damage to buildings, including Golden Gait Mercantile, a store in Ferndale, California.

“It was a strong quake, our building shook,” store owner Julie Kreitzer told The Associated Press.

“We lost a lot of stuff. I have to try to salvage something for the holidays because it’s going to be a tough year.”

In the minutes after the tremor tremor, the US National Tsunami Centre issued a warning for a long stretch of the US West Coast, from Dunes City, Oregon, south to San Francisco and San Jose, California, 640 kilometres away.

“You are in danger. Get away from coastal waters,” emergency management in San Francisco warned residents.

The City of Berkeley police department had issued an evacuation order for parts of the city on the San Francisco Bay “due to a tsunami coming to West Berkeley”, according to an alert sent to residents.

Officials with @Cal_OES are actively responding to the earthquakes this morning in Northern California.

Californians should follow guidance from local emergency responders. Get earthquake safety tips ➡️ https://t.co/gIKZPSxNaV https://t.co/Hf8DjEN3aj

— Governor Newsom (@CAgovernor) December 5, 2024

The Humboldt County Sheriff’s Office urged residents in coastal areas to evacuate immediately.

It was reported later that about 19,000 clients were without power in Humboldt County – up from near zero before the earthquake struck, according to data from PowerOutage.us.

The office of California Governor Gavin Newsom wrote on social media that he was “meeting with state emergency officials and working to ensure Californians are safe”.

“I am grateful for the robust system our state has in place that worked as intended today and kept people safe and informed,” Newsom said later on Thursday.

The US Geological Survey said aftershocks were expected.

“There is a more than 99 per cent chance of magnitude 3 and above aftershocks within the next week, and it is most likely that three to 280 of these will occur,” it said.

Geologists said there had already been dozens of aftershocks with a magnitude of 4.3 or less.

-with AAP