Parts of California have been rattled by another 4.2 earthquake that struck 100 miles east of San Diego Monday night.
The tremor follows a series of earthquakes that struck the southeastern coast of the state on Sunday.
The quakes, ranging in magnitude from 3.5 to 5.5, pushed 20 mobile homes from their foundations and triggered sporadic power outages. No major damage or injuries were reported.
Seismologists said these types of cluster quakes are common in the area. Still, the continuing aftershocks in cities like Brawley put residents on edge.
"It's not uncommon for us to have earthquakes out here, but at this frequency and at this magnitude it's fairly unusual," George Nava, the mayor of Brawley, said.
"And the fact that the aftershocks keep coming are a little alarming," he said.
Robert Graves, a geophysicist with the U.S. Geological Survey, predicted such seismic activity could possibly continue for several hours or even days.