A strong earthquake with a preliminary magnitude of 7.0 shook the coast of Northern California on Thursday, triggering a tsunami warning for millions of people.

The tsunami warnings have since been canceled, and officials from the US Geological Survey said they have not had reports of landslides or other significant damage.

Here’s what we know:

The earthquake: The epicenter of the earthquake was around 50 miles southwest of Eureka, California, in the Pacific Ocean, according to the USGS. Eureka is the largest coastal city between San Francisco and Portland, Oregon, and located about 300 miles northwest of Sacramento.

Tsunami warnings: Nearly 5 million people were under a tsunami warning from Davenport, California, up to Douglas/Lane Line, Oregon, according the National Tsunami Warning Center. This included the San Francisco Bay Area, Eureka, Fort Bragg, and Crescent City, California.

What happened: Tectonic plates well off the coast of the state moved in opposite directions, Stephen DeLong, a supervisory research geologist at the USGS, explained. That movement was likely mostly horizontal, rather than vertical — and vertical movement is the type that tends to cause tsunamis, he said. USGS data showed that the earthquake produced “severe shaking,” with residents telling CNN they felt the trembling as far south as the Bay Area.

Aftermath: More than 3,000 customers in Humboldt County, California, the closest county to the epicenter of the earthquake, are still without power, according to PowerOutage.us. That’s down from around 10,000 homes and businesses that lost service there shortly after the quake. California Gov. Gavin Newsom declared a state of emergency to help provide resources.

What officials are saying: Eureka, California, City Manager Miles Slattery said there has not been significant damage reported there so far, and described the quake as “long,” but not as “violent” as previous events. Another resident of Eureka said he felt seasick from the earthquake vibrations. There have also been no reports of injuries or damage in San Francisco, according to Capt. Justin Schorr of the city’s fire department.

What could happen next: While aftershocks are happening near the epicenter of the earthquake, it is unlikely there will be additional earthquakes of a 7 magnitude, seismologist Jeffrey Park told CNN. Still, there could be some smaller earthquakes along the faults, he said.

This post has been updated to reflect the latest power outage total in Humboldt County.

Footage captured by California resident Wren Raftery shows her backyard pool shaking Thursday in Chico, a city about 90 miles north of Sacramento.

Raftery told CNN she was in her living room when she got the earthquake alert on her phone at around 10:45 a.m. PST. She was with her 13-year-old daughter, who was at home sick.

About 10 seconds after she received the alert, Raftery said she experienced some slight shaking. She and her daughter then stepped outside to her backyard pool where she “felt the earthquake stronger.”

But Raftery said she then felt a second shaking, which she described as “mild,” about 5 minutes after the first one. This prompted her and her daughter to run back into the house. The second shaking barely lasted 10 seconds, though it left her feeling dizzy for an hour, Raftery told CNN.

“I was feeling dizzy for an hour. I felt my equilibrium was off,” Raftery said at the end of the second quake, which stopped roughly before 11:00 a.m. PST.

Raftery said she later received a message from her 10-year-old’s fifth-grade teacher informing parents that “all the students did a good job getting under their desks to be safe and were able to feel the quake.” Raftery, who was born in Chico and has lived there nearly her entire life, said that she has not heard reports of any damage in the town after speaking with her family.

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Backyard pool shakes during California earthquake

00:39 - Source: CNN