Beverly Hills earthquake hit at intersection of 2 major faults
The small earthquakes that hit Beverly Hills this week struck at the intersection of two potentially dangerous faults that run through the heart of urban Los Angeles County. Both faults could trigger a powerful magnitude 7 quake.
U.S. Geological Survey geophysicist Doug Given said the quakes occurred near the junction of the Santa Monica fault, which runs underneath Santa Monica Boulevard and near Pacific Palisades, Westwood, Beverly Hills and Santa Monica, and the Newport-Inglewood fault (which, despite its name, terminates north of Inglewood, meeting the Santa Monica fault in a T-shaped intersection).
The earthquakes that hit this week — a 3.2 on Monday, centered near Doheny Drive and Wilshire Boulevard, and a 3.4 after midnight Friday, centered near Wilshire Boulevard and Beverly Drive — were relatively shallow. "As a result, they were strongly felt," Given said.
Both faults are quite long, meaning they are capable of producing a destructive quake. Because they run underneath the Westside and western L.A. County — heavily populated areas — there is "significant population at risk because of them," Given said.
The Newport-Inglewood fault, beginning just off the Orange County coast and extending 50 miles northwest through Long Beach, Inglewood and into West Los Angeles, has been the subject of dire quake scenarios because it runs directly under some of the most densely populated areas of Southern California.
Movement along the southern part of that fault caused the 1933 Long Beach quake, a 6.3 temblor centered off Newport Beach that killed 115 people, mainly in Long Beach and Compton. That was the second-largest number of fatalities in a California temblor in recorded history. Damage to school buildings caused by that quake led to major steps toward earthquake-resistant construction in the state.
A study by the Division of Mines and Geology found that a quake along the Newport-Inglewood fault could cause blockage of the Hollywood Freeway at the overcrossings for Hollywood and Sunset boulevards, reduction of the capacity of Los Angeles International Airport to 30% for two days, the indefinite loss of 34% of all hospital beds in Los Angeles and Orange counties, the shutdown of five power plants for three days and impediments in water supplies.
A scenario simulating a 6.6 earthquake on the Santa Monica fault estimated that 54,000 buildings could be damaged and 85 would be damaged beyond repair. Under the scenario, a quake there could kill as many as 30 people and force the hospitalization of more than 200 people.
In 2009, a 4.7 earthquake centered near Inglewood shattered some windows and caused ceiling tiles to fall in a movie theater.
The two Beverly Hills quakes had no relationship to the recent large earthquake in Costa Rica.
http://latimesblogs.latimes.com/lanow/2012/09/beverly-hills-earthquake-hit-at-intersection-of-2-major-faults.html~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
USGS: Small earthquakes rattling California not related
The small earthquakes that rattled Central and Southern California early Friday aren't related to each other, nor are they predictors of larger, more dangerous quakes, scientists say.
"As far as we know, they aren't related," says Paul Caruso, a geophysicist with the U.S. Geological Survey in Golden, Colo.
Two quakes — magnitude 4.0 and 4.1 — struck Fresno County Friday morning. And about six hours earlier, a magnitude 3.4 quake was felt by thousands of people in Beverly Hills.
Neither the Fresno quakes nor the Beverly Hills quake was on the famed San Andreas Fault, which runs through California.
"California has quakes all the time," says Caruso. On average, Southern California alone has about 10,000 earthquakes each year, the USGS reports, many so small they cannot be felt.
No damage or injuries were reported in Friday's earthquakes. Caruso says significant damage usually only occurs at magnitude 5.5 quakes and above.
Additionally, while a small quake may temporarily ease stress on a fault line, it does not prevent a larger quake, according to the California Geological Survey.
Nor are the small quakes indicators of bigger events, says John Vidale, a seismologist at the University of Washington in Seattle.
But could the quakes have been triggered by Thursday's big 7.6 magnitude quake in Costa Rica?
"There might be some controversy about whether they are related, but actually we are too far away from Costa Rica for one quake to influence another that much," Caltech seismologist Kate Hutton said.
Vidale concurs: There wasn't enough energy in the Costa Rica quake to trigger other quakes as far away as California, he says. Costa Rica and Southern California are about 2,700 miles apart.
Also, on Aug. 25, an earthquake "swarm" was reported in the California desert near Brawley, a few miles north of the Mexico border. Only minor damage was reported. Again, that swarm can't be tied into Friday's quakes, Caruso says.
Contributing: Associated Press
http://www.usatoday.com/news/nation/story/2012-09-07/Small-earthquakes-rattle-California/57684050/1
__._,_.___
No comments:
Post a Comment