A strong earthquake struck off the northern California coast Thursday morning, triggering an unusual tsunami warning for northern California and southern Oregon and an evacuation of local residents and visitors.

The National Tsunami Warning Center, which is based in Alaska, issued the warning shortly after the 7 magnitude quake hit off the northern California coast about 10:44 a.m. It hit 45 miles southwest of Eureka, which lies about 100 miles south of the Oregon border. Center officials said the earthquake was shallow – about 8 miles deep – and that a swath of the coast in the two states could be affected. In Oregon, the warning covered the area stretching from Brookings and Gold Beach to Bandon, Port Orford and north of Reedsport.

The warning, which lasted about 90 minutes, was the first since 2022, when the center issued a West Coast warning following an earthquake in Tonga.

Dave Snider, a coordinator at the national warning center, said the tsunami waves this time measured about 3.5 inches around Arena Cove in California.

“It doesn’t sound like much,” he said, “but it doesn’t take much.”

Waves just a bit higher than that can cause significant damage in harbors, he said.

Snider said there had been no reports of damage.

When a tsunami strikes, local emergency managers and law enforcement are in charge of shepherding people in a tsunami zone to higher ground, Andy Bryand, a hydrologist with the National Weather Service in Portland, told the Capital Chronicle.

“The response needs to be immediate and decisive,” he said.

That’s exactly what happened in Brookings, where police immediately started to evacuate residents close to shore to higher ground, an emergency responder told the Capital Chronicle over the phone.

And in Curry County, emergency manager Jeff Hughes directed police and firefighters in Gold Beach to turn on two manually-operated warning sirens and tell everyone to evacuate immediately.

“We didn’t actually physically go in and start removing people,” Hughes said.

There wasn’t enough time to do more than send out a countywide evacuation order and get emergency responders to warn people in low-lying areas near the water, he said

“Whoever heard it and heeded it, went to high ground,” he said. “It’s a good run for folks who are paying attention, who are actually subscribed to the notification systems and are actually prepared for circumstance. There’s a vast number of people who are not, or were not, and I cannot emphasize enough, if you live on the coast, to be prepared for circumstances like this.”

The Oregon Parks and Recreation Department reacted to the warning by closing all state park beaches.

Bryant said that typically it takes about 45 minutes to an hour for a quake to trigger a tsunami and that usually the waves come in succession. He also said the fact that the quake was centered off Eureka and not the Oregon coast meant that waves would be traveling northward.

“It’s not like the waves would be coming in perpendicular to the coast,” Bryant said. “That likely will reduce the impact.”

Outside the immediate warning area, Lane County sent out a notification to inform coastal area residents that they could seek higher ground if they were concerned, said Devon Ashbridge, public information officer for Lane County.

“While it wasn’t expected that Florence would be directly impacted, we wanted them to be aware of that to make the best decision they can for their safety,” Ashbridge said.

The initial warning went right up to the county line between Douglas and Lane counties, about 10 miles from Florence. The county put out a similar alert in 2022 during an earthquake in the South Pacific, Ashbridge said.

While the alert was limited to coastal and surrounding areas, not countywide, it went to more than 22,000 contacts, Ashbridge said. Some of those, however, are duplicates because people can sign up to receive alerts by automatic phone calls, texts or emails.

“We’re of course incredibly grateful that this didn’t cause a tsunami, but we know the possibility is out there,” she said. “So these moments of panic are a good reminder to prepare.”