Originally published June 24, 2010 at 10 a.m., updated June 24, 2010 at 11:51 a.m.
SAN DIEGO A pair of earthquakes shook either end of San Diego County this morning.
First, a magnitude-3.6 earthquake struck the ocean floor southwest of the spot where the U.S.-Mexico border runs into the Pacific Ocean, according to automated seismographs and computers operated by the U.S. Geological Survey.
The 8:11 a.m. subsea quake was centered 25 miles south-southwest of Rosarito Beach, according to the USGS data. That's about 38 miles southwest of downtown Tijuana and about 50 miles southwest of San Diego.
At 10:07, a 4.0-magnitude temblor rattled the Imperial Valley and eastern San Diego County. It was an apparent aftershock to the magnitude-7.2 earthquake that struck April 2, killing two people in Mexicali and causing hundreds of millions dollars damage in Imperial County.
The late-morning shaker was centered six miles south-southeast of Ocotillo, on the San Diego-Imperial County line, about 100 miles east of San Diego.
Seismologists have in the past warned that earthquake data about quakes south of the border is not as reliable as U.S. quake data, because the California Integrated Seismic Network does not have equipment in Baja California.