Reporting from Calexico. — Residents of Calexico in the Imperial Valley were jolted awake as a 3.1-magnitude earthquake struck at 4:12 a.m. Monday.
Lights flickered and some light poles swayed as the aftershock struck the California border town. There were no immediate reports of injuries or property damage.
The quake was centered about 34 miles south-southwest of Calexico, according to the U.S . Geological Survey.
At the Best Western motel, patrons said it felt as if a large truck had backed into the outside wall, shaking furniture inside the rooms.
Calexico suffered significant damage in its aging downtown in Sunday's 7.2-magnitude quake, and many merchants were waiting until sunrise to clean up broken glass and plaster. Calexico police and border patrol agents remained on duty all night to prevent looting and a possible surge of illegal immigrants through the border checkpoint.
On the Mexican side of the border, Mexicali, a sprawling city of more than 1 million residents, remained without power or water delivery after Sunday's quake. The city's seven-story general hospital was evacuated because of damage.