The U.S. Geological Survey (USGS) said that the largest earthquake, measuring 5.5 on the Richter scale, struck the Imperial County farming town of Brawley at 1:57 p.m., the Associated Press reported.
Earlier, at 12:31 p.m., an earthquake measuring 5.3 on the Richter scale hit an area north-northwest of Brawley, followed by a 4.9 magnitude temblor, NBC News reported USGS geophysicist Paul Caruso as saying.
It all began with a 3.8 magnitude earthquake rattling Imperial County at 10.02 a.m., which was followed by a number of low-intensity temblors rocking the county and the nearby counties.
"The type of activity that we're seeing could possibly continue for several hours or even days," Robert Graves, another geophysicist at USGS, was quoted as saying by the Associated Press.
The earthquakes displaced about 20 families living in mobile homes and a shelter was opened for them at the Imperial Valley College gymnasium.
The Imperial County Public Health Department said that patients from two of the hospitals had been evacuated following power outages after the earthquakes.
The Imperial Irrigation District (IID) said there were sporadic power outages everywhere in the county. However, there was no major damage to the IID infrastructure and power had been reestablished, it said.
Earthquake swarms are common to the region. The region, known as the Brawley Seismic Zone, sees "lots of events at once, with many close to the largest magnitude, rather than one main shock with several much smaller aftershocks," the Associated Press quoted USGS seismologist Lucy Jones as saying.
The USGS said in a statement that there was an increased likelihood of continued seismic activity for at least the next 24 hours.
There was a conserve water advisory for the City of Brawley and the residents were asked "to not water their lawns, wash their cars or fill their pools until the advisory has been lifted," the Imperial County Public Health Department said.
A number of schools announced that they would be closed Monday.
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