Updated at 3:11 p.m. Thursday — A magnitude-7.0 earthquake that struck California’s North Coast Thursday morning rattled cities and triggered smartphone alerts farther afield, including in Napa County.
The National Weather Service immediately issued a tsunami warning for coastal areas closest to the quake’s epicenter, from Northern California to Oregon’s south coast. However, forecasters canceled the warnings shortly before noon, according to updates on the weather service's social media feeds.
The quake occurred at 10:44 a.m. PST off the Pacific coast, 40 miles from Ferndale in Humboldt County, according to the U.S. Geological Survey. Three smaller, nearby offshore quakes were also recorded between 11:02 and 11:10 a.m., with magnitudes between 3.3 and 4.2.
Four minutes later, the weather service issued a tsunami warning due to the possibility of the quake triggering powerful waves and strong ocean currents. The warning, issued by the Alaska-based National Tsunami Warning Center, applied to coastal areas from Davenport northwest of Santa Cruz to the border of Douglas and Lane counties in Oregon, near the coastal town of Florence.
People were ordered to stay away from coastal waters and move to higher ground inland immediately. Forecasters told people to avoid the coast until local officials deemed it safe to return.
The warnings were canceled in follow-up notices by the tsunami warning center at 11:54 a.m.
Text-message warnings connected to both the earthquake and the tsunami warning were pushed to mobile phones across Northern California, including devices in Napa County and the Bay Area.
The 7.0 quake at 10:44 a.m. was followed by an estimated 5.8-magnitude quake a few minutes later near Cobb in Lake County and a series of aftershocks after that, according to the USGS.
There were no immediate reports of injuries or major damage. But an estimated 10,000 Humboldt County residents were without power, according to the Eureka Times-Standard. Caltrans spokesperson Manny Machado said crews were checking the region’s state highways and asked motorists to avoid traveling.
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“The floor just kept moving. Our power is out,” said Eureka resident Rhonda Mitchell said minutes after the quake. “I’m pretty shook up right now.”
“Our earthquakes here aren’t rolling ones like down in the Bay Area,” said Mitchell, who lived in Milpitas for 42 years. “They shake violently back and forth, and this one felt like it just wasn’t going to stop. It’s the longest earthquake I’ve ever experienced.”
Thursday's earthquake was California’s strongest since a magnitude 7.1 quake was experienced in the Kern County town of Ridgecrest on July 5, 2019.
Gov. Gavin Newsom proclaimed a state of emergency in the North Coast counties of Del Norte, Humboldt and Mendocino to support the emergency response to the earthquake. That will allow more resources to go where they are needed, he said.
The threat posed by the quake also alarmed many coastal Bay Area residents.
Tsunami sirens wailed across Berkeley late Thursday morning, while in Oakland, computerized city signs signaled red emergency warnings for people to seek higher ground. At the Berkeley Marina, motorists streamed out as authorities shut down roads and a motorcycle officer patrolled the walkway along the West Frontage Road waterfront.
In San Francisco, workers streamed out of offices close to the water and headed up the city’s famous hills.
BART shut down the Transbay Tube after the quake, causing major delays systemwide, according to BART spokesperson Chris Filippi. Trains were running again by early Thursday afternoon.
Thursday’s quake occurred along a restless region where three tectonic plates converge, called the Mendocino Triple Junction, where the Pacific, Gorda and North American tectonic plates meet. It is considered part of the Cascadia subduction zone which extends further north along the coast; this area is known for frequent earthquake activity due to the complex plate interactions there.
None of the Bay Area's three major faults — the San Andreas, Hayward and Calaveras — had a role in Thursday's earthquake.
This story includes reporting by Napa Valley Register city editor Howard Yune, Bay City News Service, and Bay Area News Group reporters Lisa M. Krieger, Paul Rogers and Shomik Mukherjee.
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