A 4.3 magnitude earthquake struck the Tri-Valley at 1:11 p.m. Monday, followed by an aftershock 13 minutes later measuring 3.5 on the moment magnitude scale.

The U.S. Geological Survey converted from the Richter Scale, which was invented in 1935 by Caltech seismologist Charles Richter, to the moment magnitude scale.

The quake and its aftershock were centered 7 miles east of Blackhawk near Danville, and rumbled from a depth of 7 miles.

A survey of police and fire departments in Livermore, Pleasanton and Dublin showed no reports of damage in the area.