SAN RAMON — An unsettling pattern of the ground shaking often near this city continued Friday morning, when three minor earthquakes hit four minutes apart.
The U.S. Geological Survey recorded a magnitude 2.6 earthquake at 8:18 a.m.. Two minutes earlier, the USGS recorded a 2.8 quake, and at 8:14, it recorded a 3.0 tremblor.
All three of the earthquakes were centered about 2.5 miles east southeast of San Ramon. The third of the three was at a depth of about 5½ miles under the Earth’s surface and the second one was about 4¾ miles below the surface. The first quake was about 5 miles below.
The quakes add to a long list of them in the area since early November. Before Friday, the most recent of those was a 3.2 earthquake that rattled the area on New Year’s Day.
Geologists call the earthquakes a “swarm.” The earthquakes have ranged in size from 0.6 to a 4.0 quake that struck the area Dec. 19.