PETROLIA, Calif. - An earthquake with a preliminary-magnitude of 4.6 struck just off the Humboldt County coast Saturday evening, according to the U.S. Geological Survey.

The quake, which struck at 5:56 p.m., occurred on the Mendocino fault and was centered about 6 miles southwest of Petrolia and 180 miles north of San Francisco, the USGS said.

The temblor struck an extremely rural part of the state and was felt as far as the town of Blue Lake, about 50 miles north of the epicenter.

The Humboldt County Sheriff's Department said that no injuries or property damage were immediately reported.