Tsunami warning expires for Northern California after magnitude-7.0 offshore earthquake

Evacuations were ordered for several Northern California coastal communities Thursday after a magnitude-7.0 offshore earthquake triggered a tsunami warning for millions of people in parts of California and Oregon.

The strong quake was reported at 10:44 a.m. in the Pacific Ocean about 30 miles west of Petrolia in Humboldt County, the USGS reported. The quake with an initial magnitude of 6.0 that was upgraded to 7.0 generated widespread shaking along the California coast and some inland communities.

Earthquakes Oct 16

California earthquakes: Preparing for the big one

Earthquakes Sep 16

Seismologist Dr. Lucy Jones says this is most important to remember when earthquake strikes

The tsunami warning issued from Davenport, California in Santa Cruz County to the Oregon border expired at about noon. The warning area included the San Francisco Bay. Evacuation orders were issued for several communities in the warning zone and BART service was interrupted.

A tsunami warning indicates widespread water inundation is imminent, expected or occurring, according to the National Weather Service. Dangerous coastal flooding and powerful currents are possible and may take several hours to arrive.

Warnings can be downgraded to advisories and watches, or canceled based on updated information and analysis.

"We determined that we were not going to see a widespread destructive wave from it," David Snider, NOAA tsunami warning coordinator. "It didn't push or move a lot of that water toward the coast."

Snider said it wouldn't be unusual to see stronger currents and waves in the hours following the quake.

Weak to light shaking was reported in Half Moon Bay, Redwood City, Sunnyvale, San Francisco and other parts of the Bay Area, Santa Cruz, Eureka, Sacramento, Livermore and other areas.

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

Humboldt County District 2 Supervisor Michelle Bushnell told NBC News that her office has received word of broken water mains, damaged windows and houses off their foundations. The fire department was still conducting an assessment late Thursday morning.

Gov. Gavin Newsom, who was scheduled to speak at the California-Mexico border at midday, was briefed on the earthquake, his office said.

"An earthquake this size doesn't happen very frequently, but frequently enough that we need to be ready for them," said USGS seismologist Robert DeGroot.

Dozens of aftershocks, including one of magntiude-4.7, were reported in the same area off the coast.

"The earthquake was primarily strike-slip, meaning two tectonic plates slid past each other," USGS said in an X post. "These types of earthquakes are less likely to cause tsunami because their movement is primarily horizontal with minimal vertical movement of the ocean floor."

Photos: What to Keep in Your Disaster Emergency Kit

"That was quite the shaker," said Talia Flores, of the Humboldt Bay Fire Department. "It lasted a lot longer than we had anticipated."

The California Geological Survey says the California's shores have been struck by more than 150 tsunamis since 1800. Most have been small, causing a slight rise in water levels in coastal areas and little damage. But whether they're generated by local or distant sources, such as earthquakes in the Alaska Subduction Zone, tsunamis also have led to deaths and destruction in the state's waterfront communities.

On March 28, 1964, a tsunami triggered by a powerful earthquake in Alaska smashed into Crescent City hours later. Much of the business district was leveled and a dozen people were killed. More recently, a tsunami from a 2011 earthquake in Japan caused about $100 million in damages along the California coast, much of it in Crescent City.