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The U.S. Geological Survey (USGS) measured the quake at 7.2 magnitude, correcting its previous measurement of 6.9 magnitude. The quake struck in Baja California, Mexico, southeast of Mexicali, at 5:40 p.m. (2240 GMT), according to the USGS

 - By Chris Smith -

The San Onofre Nuclear Generating Station  in Southern California remained intact after a 7.2-magnitude earthquake shook the region on Sunday, authorities said.  The earthquake did not result in the shutdown of the San Onofre Nuclear Generating Station in the region, said Southern California Edison, a public electricity facility.

The San Onofre Nuclear Generating Station (SONGS) is jointly owned by Southern California Edison (SCE) (78.21%), San Diego Gas & Electric (20%), and the city of Riverside (1.79%). Today, SONGS generates approximately 2,200 megawatts of power, enough to serve 1.5 million average Southern California homes at a point in time.

The U.S. Geological Survey (USGS) measured the quake at 7.2 magnitude, correcting its previous measurement of 6.9 magnitude. The quake struck in Baja California, Mexico, southeast of Mexicali, at 5:40 p.m. (2240 GMT), according to the USGS.  The quake rocked all of Southern California, and sent high rise buildings in Los Angeles and San Diego rocking back and forth.

The nuclear plant is built to withstand a 7.0 earthquake 5 miles (8 km) away, according to San Diego Gas & Electric (SDG&E). The earthquake caused "low-level ground movement" at the nuclear plant, said spokesman Gil Alexander.

The San Onofre Nuclear Generating Station (SONGS) is located next to San Onofre State Beach, which adjoins the Camp Pendelton U.S. Marine Corps Base in northern San Diego County. The plant contains three nuclear reactors, units 1, 2, and 3. Units 2 and 3 are currently in use and are capable of producing enough power to serve the needs of 2.75 million households (that is, 2,254 megawatts of power). When both SONGS units are operating, they have the potential of saving the equivalent of 188 billion cubic feet of natural gas each year. Unit 1 was retired in 1992 after 25 years of service and is currently being decommissioned.

"The movement was not sufficient to prompt a shut-down, but it did trigger a regulatory protocol ...(and) plant personnel have begun inspections conducted in such situations," Alexander said. "Operators would be able to shut the units down without any danger to the public. Today's quake occurred several hundred miles from the facility."

Nearly 2,400 customers lost power in Dana Point, just inside the Orange County line near Los Angeles, according to Jennifer Ramp of SDG&E.  In San Diego County, more than 600 customers lost power in Borrego Springs when the earthquake struck, Ramp said.  Smaller outages were also reported in some areas in Southern California.

Three strong jolts including a magnitude-5.1 aftershock were felt in the Imperial County desert east of San Diego in the hour after the magnitude-7.2 quake struck.  Magnitude-4.5 and magnitude-4.3 aftershocks came before and after. In Los Angeles, five stalled elevators were reported, but it was unknown whether any of the incidents were related to the quake, said Erik Scott of the Los Angeles Fire Department.

The city fire department went on earthquake status, and is inspecting buildings and overpasses for damage, he said.  LA City fire helicopter crews report that they have finished an initial assessment and see no damage, no fires, and all reservoirs are holding water normally.

The earthquake was also felt in Phoenix and Las Vegas, residents there said. A police dispatcher in Yuma, Arizona, said the quake was very strong there, but no damage was reported.

The epicenter for the quakes was under a small volcanic caldera that last erupted about 10,000 years ago, located about 20 miles ( 32 kilometers) southeast of the border crossing between Calexico, California, and Mexicali, Mexico.

The caldera, which is home to a large geothermal power plant, has been delivering small-to-moderate quakes for the past several months.