SAN FRANCISCO — A magnitude 7 earthquake about 30 miles off Humboldt County prompted a highly unusual tsunami warning for a wide swath of the Northern California coast Thursday, spurring widespread evacuations before it was canceled an hour later.

The earthquake rattled large parts of the region — from San Francisco and Monterey to as far away as Sacramento, Reno and southern Oregon — providing a stark reminder of how coastal seismic activity can threaten to produce damaging tsunamis under the right circumstances.

While many reported terrifying shaking in and around the Eureka area, there were no immediate reports of severe damage or major injuries, likely owing in part to the epicenter being so far away from highly populated areas. Preliminary estimates indicate the epicenter was about 55 miles southwest of Eureka, 48 miles southwest of Fortuna, 40 miles northwest of Petrolia, and 100 miles northwest of Mendocino.

But while damage from the quake itself may have been relatively light, shaking of this strength is a reminder of the tsunami risk in California — particularly from nearby earthquakes that provide far less warning time to evacuate beaches and low-lying areas. Some of the most memorable damaging, and sometimes deadly, tsunamis in the last few decades occurred from earthquakes that started much farther away from land, such as in Japan, Alaska and Hawaii.

Thursday’s earthquake occurred at 10:44 a.m. Pacific time. “Very strong” shaking, as defined by the Modified Mercalli Intensity Scale, was felt in the Humboldt County communities of Petrolia and Ferndale. “Very strong” shaking is generally capable of causing considerable damage to poorly built or badly designed structures, according to the U.S. Geological Survey.

The USGS said “moderate” shaking was felt in Eureka, a level generally strong enough to break windows and dishes.

The tsunami warning was canceled just before noon.

But the hour or so it was in effect was marked by intense anxiety as jurisdictions across the Northern California coast issued evacuation orders for low-lying areas. BART, the commuter rail system for the San Francisco Bay Area, suspended service through the underwater Transbay Tube connecting San Francisco and Oakland because of the tsunami warning. Guests at the San Francisco Zoo, near the coast, were ordered to evacuate, with animals secured and staff moved to higher ground.

Even communities far from the coast took action. All schools in Davis, California, were ordered evacuated because of the shaking.

Olivia Cobian, the innkeeper at the Gingerbread Mansion, a bed and breakfast in the historic town of Ferndale, said her 1895 building “looked like a war zone.”

“I have fireplaces flying forward.” she said. “Clawfoot tubs that have been lifted off (their mounts) and scooched over. This is crazy.”

Cobian said that moments before the quake struck, she had been giving a tour of the inn to a third-grade class from the local elementary school.

“They had just walked” back to school, she said, adding, “Thank God.”

“It’s insane,” she said, walking through the inn surveying the damage. Then, in the background, a siren began to wail. Cobian said she had to go talk to firefighters who had appeared.

The shaking at the Petrolia General Store was intense and lasted for about 10 seconds, according to employee Kaitlin Graves.

“It was a big earthquake. It was a lot of up-and-down shaking,” Graves said in a phone interview. “It felt like the woozy feeling you get when you’re in an elevator.”

The shaking was so intense it knocked off several objects off the shelves, and multiple glass items shattered, Graves said.

Humboldt County Supervisor Rex Bohn, whose district includes the earthquake zone, said there has been no major damage reported so far.

“I just talked to one of our local hospital providers ... and they seem to be doing OK,” he said.

“It’s a mess. There’s a lot of stuff off the shelves,” he added, but that seemed to be the extent of the damage at this point.

Bohn said the earthquake hit the Scotia and Rio Dell/Mattole Valley region of Humboldt County, almost exactly the same location an earthquake hit in 2022.

“It was a sudden jolt and it rolled out,” Bohn said.

The 2022 temblor, a magnitude 6.4, struck near Eureka, killing two and injuring 11 people. The powerful jolt caused widespread power outages and damage.

The force of the shaking shattered windows, sent objects flying and damaged at least one historic bridge in the small communities south of Eureka.

Steve Wells, a spokesman for the Fort Bragg Fire Department, said shaking in the coastal town was minimal and no damage had been reported. He said out of precaution, many residents were moving their boats out of the harbor in case of a sea swell.

In the community of Manila on Humboldt Bay, Jennifer Savage said she and her neighbors felt a long, rolling quake.

“People are pretty freaked out,” said Savage, who works at the Surfrider Foundation.

When the quake hit, a crew of workers from the Pacific Gas and Electric Co. were perched high in the air, working on power lines. They swayed in the sky during the quake, she said.

A nightmare scenario for California would be something like the disaster that occurred in 1812, when a large earthquake in the Santa Barbara area “was followed by a tsunami that wiped out many coastal villages and destroyed ships in the harbor,” according to the USGS.

Another scenario involves an earthquake in the Santa Barbara Channel that could spawn tsunamis in Carpinteria, Santa Monica and points farther south. Some neighborhoods close to the coast in other tsunami scenarios — such as Balboa Island in Newport Beach — could struggle to evacuate, especially if there are only narrow roads around to evacuate.

An average of five earthquakes with magnitudes between 7.0 and 8.0 occur per year in California and Nevada, according to a recent three-year data sample.

The earthquake occurred at a depth of 6.2 miles.

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