The 6.5 magnitude temblor hit at about 4.27pm PST Saturday (12.27am GMT) and was centred in the Pacific about 35 kilometres west of Ferndale, but was felt as far south as Capitola in central California and as far north as central Oregon, the US Geological Survey said.
In Eureka, 386 kilometres north of San Francisco, residents of an apartment building were evacuated, and an office building and two other commercial structures were declared unsafe for occupancy, according to Humboldt County spokesman Phil Smith-Hanes.
“Our initial reports were that, though this was a pretty decent quake, we survived it well,” Smith-Hanes said, adding that damage assessments would take place across the county yesterday.
More than a dozen aftershocks, some with magnitudes as powerful as 4.5, rumbled for several hours after the initial quake, which had a depth of nearly 15 kilometres.
Authorities said no major injuries have been reported. But several people received minor cuts and scrapes from broken glass at the Bayshore Mall in Eureka, and an elderly person fell and broke a hip, authorities said.
“We’re mostly getting reports of bumps, bruises and hits on the head,” said Laurie Watson Stone, a spokeswoman for St Joseph Hospital, a 146-bed hospital in Eureka.
“The emergency room is busy, but we haven’t heard of any major injuries.”
Amanda Nichols, a dispatcher for Eureka Police Department, said she received a report that an infant was struck in the head with some flying debris at the mall.
Pacific Gas & Electric Co spokesman JD Guidi said power outages were widespread across most of Humboldt County, affecting about 25,000 customers. Nearly 10,000 remained without power some five hours after the quake, and it was expected many could still be without power yesterday, said PG&E spokeswoman Janna Morris.
No damage was done to the company’s former nuclear power plant outside Eureka, Morris said.
Several traffic lights fell and numerous residents reported water, gas and sewer leaks, Humboldt County Office of Emergency Services spokeswoman Jo Wattle said.
“People have chimneys down, and we’re hearing about minor property damage and lots of glassware broken,” Wattle said.
It struck in an area where earthquakes ranging from 7.0 to 7.3 have struck periodically since the 1800s.