A Eureka, Calif., police officer walks across the damaged porch of a house that was knocked off its foundation by Saturday's magnitude-6.5 earthquake. (Josh Jackson/The Times-Standard/Associated Press)

Government employees, engineers, volunteers and home and business owners were out examining everything from bridges to buildings in northern California's Humboldt County on Monday, checking for damage caused by a weekend earthquake.

Residents swapped stories about enduring the magnitude-6.5 quake, centred in the Pacific Ocean about 35 kilometres west of Ferndale.

In Eureka, the largest city affected by Saturday's temblor, a city inspector posted a red tag outside a home that had shifted off its foundation and dropped one metre into the crawlspace below, forcing its owners to stay with friends. The tag indicated the single-family, wood-frame home was uninhabitable. Yellow tags elsewhere meant buildings were damaged but inhabitants could stay put.

The city-wide damage estimate climbed to $14.3 million US for 175 buildings, city spokesman Gary Bird said. Officials said it might be several days before they have a complete estimate for the entire county.

The earthquake sent about 30 people to emergency rooms, but only one was seriously injured — an elderly person who fell and suffered a broken hip.

Power outages were widespread, affecting about 36,000 customers, but electricity was restored to all by early Sunday, said Janna Morris, a spokeswoman for Pacific Gas & Electric.

In Ferndale, the owner of The Blacksmith Shop gallery was at work when the quake hit. Joseph Koches, 72, said he dropped to the floor and crawled to a doorway he had reinforced with iron after a 1992 earthquake.

Koches estimated his damage at between $25,000 and $35,000 US for at least 150 pieces of glass artwork, broken windows and display cases.

"This was 150 pieces of glass going up in the air and falling and breaking, and glass cases going over," he said. "If you can imagine some giant coming along and picking up your building and shaking it. And you have no control. Things just start coming down around your ears."

With files from The Associated Press