A magnitude 6.4 earthquake shook parts of Northern California early Tuesday, knocking out power to thousands of people.
The quake struck at a depth of 10 miles shortly after 5:30 a.m. ET near Eureka in Humboldt County, the U.S. Geological Survey said.
It impacted about 7.4 miles west-southwest of Ferndale, the agency said.
More than a dozen smaller earthquakes appeared to hit parts of the region afterward, he said.
It was not immediately known if anyone was injured in the quake.
More than 70,000 utility customers were without power in Humboldt County as of 8 a.m. ET Tuesday, according to online outage tracker Poweroutage.us.
“Power is out throughout the entire county,” the Humboldt County Office of Emergency Services said in a tweet, adding, “DO NOT CALL 911 UNLESS YOU ARE EXPERIENCING AN IMMEDIATE EMERGENCY.”
There was no tsunami threat associated with the quake early Tuesday, the National Weather Service’s tsunami warning system said.
Several people said on social media that they were woken up by the MyShake earthquake warning app on their mobile phones.
The quake comes almost exactly one year after a 6.2-magnitude earthquake struck off the coast of the Cape Mendocino area in northern California on December 21 last year. No major damage or injuries were reported in connection with this earthquake.
That earthquake had occurred at a depth of 5.6 miles in the Pacific Ocean, about 24 miles west of the small community of Petrolia along the Rocky Desert of California’s Lost Coast region in the county of Humboldt, the Geological Survey and the Humboldt County Sheriff’s Department said at the time.
This is a developing story. Check back for updates.
Chantal Da Silva is a breaking news editor for NBC News Digital based in London.