Small Probability of Larger Event Following Friday’s Calif. Quake

March 31, 2014

In an announcement detailing the specifics of a 5.1 magnitude earthquake that struck Southern California on Friday, AIR Worldwide said there is a 5 percent probability that the earthquake could be a foreshock to a larger event.

AIR said the probability was reported by United States Geologic Survey seismologists.

AIR reported that Friday’s event rattled several counties including Los Angeles, San Bernardino, Orange, Ventura, and Riverside.

The quake occurred at a relatively shallow depth of 4.6 miles (7.5 km) and its epicenter was located in northern Orange county, approximately 3 miles (5 km) north of the city of Fullerton, according to the USGS, AIR said.

Two foreshocks preceded the quake about an hour prior, and more than 100 aftershocks were reported since, AIR said in its statement on Sunday.

According to preliminary analyses from the USGS, the causative fault may be the Puente Hills Thrust, a blind thrust fault that was the source of the 1987 Whittier Narrows M5.9 earthquake. The fault extends northwestward into downtown Los Angeles, and seismologists believe that a major event on this fault could result in catastrophic damage in the Los Angeles metropolitan area.

The average recurrence interval of a large rupture (~M7.5) of the thrust fault is estimated to be once every several thousand years.

During Friday night’s earthquake, five houses and 20 apartments were damaged in Fullerton, and officials are examining whether they have been structurally compromised.

According to AIR, the shaking has caused minor damage to the contents of homes and business, but no significant damage or injuries have been reported at this time.

Source: AIR Worldwide