The quake struck at 10:08PDT with an epicenter in Julian, California.

Governor Gavin Newsom's office posted on X shortly after the quake that he had been briefed on the situation.

"The state is coordinating with local authorities to assess any damage and if emergency response is needed," the statement said.

Emergency alerts ordered residents to take shelter as far away as Los Angeles.

"Drop, cover, hold on. Protect yourself," the alert read.

Julian, a resort town with gold rush roots, is located in the Cuyamaca Mountains about an hour northeast of San Diego.

The USGS continued to report smaller aftershocks in the region in the hour after the quake. (BBC/NBC)