There have been several sizable aftershocks, including a magnitude 5.2 earthquake.

A second earthquake on a different epicenter registering a 6.0 on the Richter scale struck 5.6 miles WNW of Cobb, California 4 minutes later.

A tsunami warning was issued for coastal areas in Oregon and Northern California.

"The first waves are expected to arrive at 12:10 p.m. for San Francisco Bay Area, Karleisa Rogacheski, a meteorologist for the weather service told SFGATE. In areas farther north, such as Fort Bragg, the waves could come sooner, she said. Rogacheski said the weather service is still assessing the wave heights and severity, but advised people to stay away from the water.