A magnitude 4.8 earthquake occurred near El Centro in Imperial County at 12:36 a.m. Monday, producing shaking across much of San Diego County, including in coastal cities, according to the U.S. Geological Survey.
The agency said the mainshock was followed 6 minutes later by a magnitude 4.5 aftershock and a series of smaller aftershocks, all of which originated west of the Salton Sea.
The epicenter of the mainshock was 11.7 miles deep, at a point roughly 113 miles east of San Diego. The quakes appear to have been caused by the San Jacinto fault system, one of the most active faults in Southern California.
The fault system runs through parts of Imperial, San Diego, Riverside and San Bernardino counties. On Dec. 25, 1899, the San Jacinto produced a magnitude 6.7 quake that was felt throughout much of Southern California.
This story originally appeared in San Diego Union-Tribune .