SAN FRANCISCO (AP) — Valerie Starkey was driving through Northern California to visit relatives when she suddenly felt shaking and feared her car had broken down, only to realize later that it was an earthquake so powerful that it triggered a tsunami warning for hundreds of miles of the U.S. West Coast.

The epicenter of Thursday’s 7.0 magnitude shaker occurred in what’s known as California’s “earthquake country” because it’s where three tectonic plates meet. The temblor was the most powerful to rattle the state since a 7.1-magnitude quake hit Ridgecrest in 2019.

Its intensity shocked Starkey and many of the 5.3 million other people along nearly 500 miles (805 kilometers) of the California and Oregon coasts who were under the tsunami warning for about an hour. It was lifted after no major waves arrived.

“I thought my axles had fallen apart,” said Starkey, a Del Norte County supervisor representing Crescent City, a town of fewer than 6,000 near the Oregon border. “That’s what I was feeling … ‘My axles are broken now.’ I did not realize it was an earthquake.”

The quake struck at 10:44 a.m. west of Ferndale, a small city in coastal Humboldt County, about 130 miles (209 kilometers) from the Oregon border, the U.S. Geological Survey said. The shaking knocked items off grocery store shelves and sent children scrambling under desks at schools.

It was felt as far south as San Francisco, some 270 miles (435 kilometers) away, where residents described a rolling motion for several seconds. It was followed by multiple smaller aftershocks. There were no immediate reports of major damage or injuries from the quake.

The tsunami warning issued shortly after the quake struck spanned from the edge of California’s Monterey Bay north into Oregon.

“It was a strong quake. Our building shook. We’re fine, but I have a mess to clean up right now,” said Julie Kreitzer, owner of Golden Gait Mercantile, a store packed with food, wares and souvenirs that is a main attraction in Ferndale.

“I have to go. I have to try and salvage something for the holidays because it’s going to be a tough year,” Kreitzer said before hanging up.

The region — known for its redwood forests, scenic mountains and the three-county Emerald Triangle’s legendary marijuana crop — was struck by a magnitude 6.4 quake in 2022 that left thousands of people without power and water. The northwest corner of California is the most seismically active part of the state because it’s where three tectonic plates meet, seismologist Lucy Jones said on the social media platform BlueSky.

Shortly after the quake, phones in Northern California buzzed with the tsunami warning from the National Weather Service that said: “A series of powerful waves and strong currents may impact coasts near you. You are in danger. Get away from coastal waters. Move to high ground or inland now. Keep away from the coast until local officials say it is safe to return.”

Numerous cities urged people to evacuate to higher ground as a precaution.

In Santa Cruz, authorities cleared the main beach, taping off entrances with police tape. Aerial footage showed cars bumper-to-bumper heading to higher ground on California highways 1 and 92 in the Half Moon Bay area south of San Francisco.

Cindy Vosburg, the executive director for the Crescent City-Del Norte County Chamber of Commerce, said she heard alarms sound just before shaking began, and the city’s cultural center downtown started to creak.

“Just as it would start to subside, the building would roll again,” Vosburg said.

White House spokesperson Jeremy Edwards said President Joe Biden was briefed on the earthquake and that FEMA officials are in touch with their state and local counterparts in California and Oregon.

Gov. Gavin Newsom signed off on a state of emergency declaration to quickly move state resources to impacted areas along the coast. State officials were concerned about damage in the northern part of the state, Newsom said.

Crews in Eureka, the biggest city in the region, were assessing if there was any damage. Eureka Mayor Kim Bergel, who works at a middle school, said lights were swaying and everyone got under desks.

“The kids were so great and terrified. It seemed to go back and forth for quite a long time,” she said. Some children asked, “Can I call my mom?”

The students were later sent home.

Humboldt County Sheriff William Honsal said residents experienced cracks in their homes’ foundations, as well as broken glass and windows, but nothing severe.

Honsal said he was in his office in the 75-year-old courthouse in downtown Eureka when he felt the quake.

“We’re used to it. It is known as ‘earthquake country’ up here,” he said. “It wasn’t a sharp jolt. It was a slow roller, but significant.”

The San Francisco Bay Area Rapid Transit District, known as BART, stopped traffic in all directions through the underwater tunnel between San Francisco and Oakland, and the San Francisco Zoo’s visitors were evacuated.

This quake was a strike-slip type of temblor that shifts more horizontally and is less prone to cause tsunamis, unlike the more vertical types, said National Weather Service tsunami program manager Corina Allen in Washington state.

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Dazio reported from Los Angeles. Associated Press writers Christopher Weber, Jaimie Ding and Dorany Pineda in Los Angeles; Martha Mendoza in Santa Cruz, California; Sophie Austin and Tran Nguyen in Sacramento, California; and Seth Borenstein in Washington, D.C., contributed to this report.