SAN FRANCISCO, USA - A strong 6.0 magnitude earthquake struck offshore Northern California on Thursday, but there were no injuries or damage to buildings reported.

The quake struck at a depth of seven miles (11.2 km) at a distance of 35 miles (56 km) west-northwest of Petrolia, California, the United States Geological Survey said.

The temblor failed to trigger a tsunami warning and local police and fire officials did not expect to receive reports of damaged structures or injuries, according to a police spokesman in Eureka, the biggest town near Petrolia.

'Spilled coffee is about the worst thing,' said Lt. Murl Harpham of the Eureka Police Department.

A magnitude 6.5 temblor struck off the coast of Eureka on January 9, damaging some buildings in the city's downtown, knocking at least one house off its foundation and forcing more than 120 homeowners to begin taking down unsafe chimneys, Harpham said.