4.0 San Diego County Quake

At 8:18 p.m. Monday evening a magnitude 4.0 earthquake occurred about 14 miles east-southeast of Julian in San Diego County, according to the United States Geological Survey.

In maps provided by USGS the earthquake was felt throughout much of east San Diego County, north into the Hemet area, west into the city of San Diego and felt south in Tijuana.

There have been no reports of damage or injuries.

According to data by USGS it appears this earthquake was located right on the Elsinore Fault Zone.

The Elsinore Fault Zone, which has the potential to produce an earthquake between magnitude 6.5-7.5, has been rather puzzling to many geologists as for being one of Southern California's largest faults it has remained "quiet."

The last notable earthquake on this fault occurred on May 15, 1910 when a magnitude 6.0 occurred near Temescal Valley.

The interval between major ruptures on the Elsinore Fault, according to the Southern California Earthquake Data Center, is about 250 years. The last major rupture was during the 18th Century.

Beginning south the fault begins southeast of Julian, just north of I-8, moving northwest running just under the I-15/I-215 interchange in Murrieta, then paralleling I-15 and finally splitting into the Whittier Fault and Chino Fault in Corona (of which both faults cross the 91 freeway).

While no doubt a threat to the cities and communities along the I-15 the Elsinore Fault is, behind the Newport-Inglewood Fault, a major threat for Orange County.

At 10:08 p.m. there was a small 2.5 aftershock, according to USGS.