SAN DIEGO -- A magnitude 3.6 aftershock struck the Imperial Valley and eastern San Diego County Sunday, according to automated seismographs and computers operated by the U.S. Geological Survey.

The aftershock was centered about 25 miles south of Mexicali, or about 120 miles east of San Diego. It hit at 9:01 a.m.

Thousands of similarly-sized aftershocks have rattled the area since a magnitude 7.2 earthquake struck April 2, killing two people in Mexicali and severely damaging canals, schools and older buildings in Imperial County.