March 23, 2009
By Stevie Smith
The Tech Herald
Seismologists are monitoring a swarm of small earthquakes that are occurring near the southern San Andreas fault, a seismic zone capable of causing the proverbial “Big One,” an event large enough to inflict widespread death and destruction in Orange County.
Photo: How hard the southern San Andreas fault might shake certain areas in a big quake.
In a rare an unusual statement, the Scripps Institution of Oceanography says, “A swarm of earthquakes is trembling through Southern California near the Salton Sea (the southern end of the fault). Over 40 small earthquakes, ranging from magnitude 1 to magnitude 3, shook the region over the weekend and continue today.
“While earthquake swarm events are not precursors or indicators of a larger earthquake event, they are jolting reminders that Southern California will experience the Big One soon.”
Graham Kent, a Scripps reearch geophysicist, said during a phone interview that, “A lot of other faults have been discovered in the Salton Sea in recent years. We’re trying to understand how they’re interconnected and if they could lead to something like the Elmore Ranch quake. If we suddenly started having quakes in the 5.0 to 6.0 range in the Salton Sea, we’d wonder if they’d be a precursor to something bigger.”
On November 23, 1987, Southern California shook hard from the 6.2 Elmore Ranch quake, an event tied to the 6.6 quake at Superstition Hills the following day. Such quakes have been reminders of the potentially catastrophic seismic energy that could hit Southern California.
In fact, it was just that sort of concern that led seismologists to produce a scenario 7.8 quake on the southern San Andreas. Scientists said such a quake could kill more than 300 people and injure more than 9,000 in Orange County, and cause the ground to move 3 feet in Buena Park. The scenario was produced for the Great Southern California Shakeout, the largest earthquake drill in U.S. history. The scenario was not based on evidence that the “Big One” is about to happen, only that it will at some unknown point in the future.
In today’s news release, Scripps added that, “Scientists believe the Salton Sea and surrounding region is the most seismically active regionof the world and should experience a large earthquake sooner rather than later if the region follows historiical patterns.
“Recent work by by Scripps geophysicists Graham Kent, Neal Driscoll, and Jeff Babcock suggests that large magnitude 7 earthquakes on the San Andreas fault have occurred roughly every 200 years in the region, yet it has been largely silent for the last 335 years.”
http://sciencedude.freedomblogging.com/2009/03/23/san-andreas-twitching-with-quakes-that-could-affect-oc/22663/