A magnitude 7 earthquake struck off the northern California coast, triggering an instant tsunami warning for hundreds of km along the California and Oregon coast. According to the US National Weather Service, the tsunami warning affected around 4.7 million people in California and Oregon until it was lifted.

The quake struck Thursday (local time) at a shallow depth of 10 kilometres and was centred around 65 kilometres west of Ferndale, a sparsely inhabited area of the northern California coast, according to the US Geological Survey. It was the largest earthquake in the region since a 7.2 magnitude tremor in 2005. Tens of thousands of people reported feeling the tremor, with signs and chandeliers swinging back and forth. People reported sloshing and spilling water in their residential pools.

There were no initial reports of significant injuries, although the tremor damaged some structures, including Golden Gait Mercantile in Ferndale, California. “It was a strong quake, and our building shook,” store owner Julie Kreitzer told the AP. “We lost a lot of things. I have to attempt to salvage something for the holidays since this is going to be a difficult year.”

In the minutes following the tremor, the US National Tsunami Centre issued a tsunami warning for a broad stretch of the US West Coast, from Dunes City, Oregon, south to San Francisco and San Jose, California, 640 km distant. “You’re in danger.” “Avoid coastal waters,” San Francisco emergency management told citizens. According to an advisory sent to citizens, the City of Berkeley police department issued an evacuation order for areas of the city on the San Francisco Bay “due to a tsunami coming to West Berkeley”.

The Humboldt County Sheriff’s Office advised citizens in coastal areas to evacuate immediately. According to data from PowerOutage.us, over 19,000 clients in Humboldt County were without power, up from nearly zero before to the earthquake. California Governor Gavin Newsom’s office stated on social media that he is “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 added a few hours later. According to the US Geological Survey, aftershocks are likely. “There is more than 99 percent possibility of magnitude 3 or higher aftershocks during 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.