Dozens of small to moderate earthquakes rattled Southern California, shaking an area from rural Imperial County to the San Diego coast and north into the Coachella Valley.
The largest quake, magnitude 5.3, struck at 12:31 pm (local time) yesterday about five kilometres north-northwest of the small Imperial County farming town of Brawley, according to Paul Caruso, a geophysicist with the US Geological Survey. It was followed minutes later by a 4.9 magnitude quake.
The first quake was a magnitude 3.9 that hit at 10:02 am (local time) It was followed by a 3.4 quake about 90 seconds later in the same area near the southern end of the Salton Sea. Magnitude 2.2 and 2.0 quakes followed within six minutes of the first shock.
The USGS says at least 25 aftershocks of struck the same approximate epicenter about 26 kilometres north of El Centro.
Some shaking was felt on the coast in Del Mar, some 193 kilometres from the epicentre, as well as in southern Orange County and parts of northern Mexico.
An Imperial County sheriff's dispatcher said there were no reports of damage or injuries.
Scientists aren't yet sure what fault the quake cluster was on but it was near the 1,300-kilometre San Andreas Fault, Caruso said.