SAN DIEGO -- A 3.7-magnitude earthquake struck the Mexicali area of Baja California Saturday, but it went unnoticed in San Diego's East County, authorities said.

The quake hit at 2:51 p.m., with its epicenter about 18 miles southeast of Mexicali, the state capital of Baja California. It was located about 120 miles southeast of downtown San Diego, according to automated seismographs operated by the U.S. Geological Survey.

San Diego County fire dispatchers and sheriff's officials reported no incidents related to the latest earthquake.

Separately, three minor quakes also rattled the Imperial Valley and eastern San Diego County overnight, the automated equipment indicated. A 3.4 magnitude quake struck at 7:18 p.m. Friday, followed by a 3.0 quake at 4:03 a.m. and a 2.7 magnitude quake at 6:47 a.m. Saturday.

A rash of earthquakes of about that size have rattled the area for the past two weeks. Three of them have exceeded magnitude 5.0, including one last Tuesday afternoon that was felt in downtown San Diego, 110 miles away.

The rash of quakes is occurring deep beneath a section of the San Andreas Fault system known for earthquake swarms. Similar incidents have occurred in recent years.

Minor damage from the swarm has been reported in Mexicali, where schools and businesses have suffered structural cracks, and electric power disrupted by the earth movement.