Earthquake swarm: Series of temblors could continue to rattle Salton Sea area for several days

WESTMORLAND, Calif. (KABC) -- An earthquake swarm continued Thursday in desert communities near the Salton Sea, which has a history of such seismic activity, and the series of temblors could continue for several days.

The hundreds of earthquakes included a magnitude-4.9 tremor Wednesday afternoon, according to the U.S. Geological Survey.

There were 28 quakes alone from 11 p.m. Wednesday through 10 a.m. Thursday ranging in magnitudes of 2.5 to 3.6.

RELATED: Dozens of earthquakes hit in swarm near Salton Sea area

EARTHQUAKE SWARM: At least 240 small earthquakes, the largest measuring 4.9, shook desert communities near the Salton Sea Wednesday.

The swarm is centered beneath agricultural fields south of the Salton Sea, about 2.5 miles northeast of the small town of Westmorland.

"When you have a lot of earthquakes, you tend to have a lot of earthquakes," seismologist Dr. Lucy Jones said. "But it doesn't make it more likely for it to trigger somewhere else. This doesn't make us worry about the San Andreas fault; its too far away."

However, the shaking was also felt in San Diego and Riverside counties, but so far there are no reports of major damage there

Dr. Jones says the zone is a common source of swarms, and this is one of the largest ever.

Notable past seismic activity in the region includes a 1981 swarm that included a magnitude 5.8 quake and a 2012 swarm that produced a magnitude 5.4 quake, the USGS said in a statement.

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Past swarms have remained active for up to 20 days, but the average is about a week, the USGS said.

The USGS said during this earthquake swarm, the probability of larger earthquakes in that area is significantly greater than usual.

The state on Thursday coincidentally launched a "Don't Get Caught Off Guard" campaign to raise awareness of California's earthquake warning system which detects the start of a quake and sends alerts so that people can protect themselves before shaking arrives.

The annual Great California ShakeOut, in which millions of people practice the "drop, cover, hold on" response to earthquakes, is scheduled for Oct. 15.

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ABC7 has compiled a list of items that are important to have in your earthquake kit so that you're prepared for "the big one."

The Associated Press contributed to this report.