A magnitude-4.7 earthquake shook San Diego County just before 10 a.m. on Monday and was felt throughout Southern California.
The U.S. Geological Survey reported the quake was centered along the San Jacinto fault, 12 miles east/southeast of Anza, California, 14 miles southwest of La Quinta and 16 miles south-southwest of Palm Desert.
The San Jacinto is the most active fault in Southern California and runs parallel to the San Andreas Fault, said Kenneth Hudnut, a geophysicist with the U.S. Geological Survey (USGS).
Hudnut said that area has a history of large seismic events.
"It seems there’s a section of the fault near Anza that’s ready to go in a larger earthquake," said Hudnut. "So this activity is close in to that zone that is considered to be primed and ready."
There were eight earthquakes of a magnitude-6 or higher along the San Jacinto Fault in the 20th Century.
The last significant quake to strike the San Jacinto was a magnitude 5.4 temblor in July of 2010.
Hudnut said more aftershocks can be expected, and there is a 5 percent chance that this was a foreshock to something larger.
"We're in a heightened state of awareness right now. When we have a sequence like this we always are," he said.
Hudnut said the quake is a good reminder to be prepared. "Think about how much water they have stockpiled at home. Think about is their earthquake kit all stale food by now? Would they want to eat it?"
Monday's quake was originally registered as a magnitude-5.2, but was downgraded a short time later by USGS.
