The series of temblors began shortly before 11 a.m. Saturday, with the largest -- a magnitude-5.3 quake -- occurring at 10:55 a.m. at a depth of 3 miles, the USGS said. The epicenter of that earthquake was located about 7 miles west of Calipatria and 25 miles north of El Centro, a city just north of the U.S.-Mexico border.
A magnitude-4.3 quake was also among the several dozen recorded in the area Saturday morning, the USGS said.
Several hundred people from as far away as San Diego and Yuma, Arizona, reported on the USGS's website that they felt the temblor but nearly all indicated the shaking was weak.
A message from the USGS ShakeAlert early warning system was sent out 6.6 seconds after the largest quake in the swarm began, the agency said.
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Meanwhile, more than a dozen quakes -- many ranging from a magnitude-2.5 to a 3.2 -- hit the Calipatria area overnight.
The Imperial County Sheriff's Office said there were no immediate reports of injuries or serious damage from any of the temblors.
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The Associated Press contributed to this report.