The tremor was estimated to have a depth of 9.4 km (5.8 miles).
A 5.6 magnitude earthquake struck 5 kilometres (3.1 miles) south-southwest of the small community of Petrolia in northern California on Saturday evening, according to the U.S. Geological Survey. The tremor was estimated to have a depth of 9.4 km (5.8 miles). There was no immediate report of damage or casualties.
Petrolia, in Humboldt County, has an estimated population of a few hundred people, and is located 407 km (253 miles) north of San Francisco in a wilderness area that experiences frequent earthquake activity.