Southern California earthquake related to April’s Baja quake; no major damage or injuriesBy Raquel Maria Dillon, AP
Thursday, July 8, 2010
S. California earthquake related to Easter temblor
LOS ANGELES — An earthquake that briefly halted rides at Disneyland and toppled wine bottles at desert resorts happened on one of two faults that are under increased pressure because of the powerful Easter Sunday temblor in Mexico, seismologists said.
Wednesday’s magnitude-5.4 quake, centered in mountain wilderness 30 miles south of Palm Springs, rattled buildings more than 100 miles away in downtown Los Angeles, but no major damage or injuries were reported.
The latest quake occurred in the San Jacinto fault zone — one of two fault lines where researchers have noticed increased pressure since April’s magnitude-7.2 quake that killed two people in Baja California. More than 5,000 aftershocks have rattled the border region since then.
The San Jacinto fault is the most seismically active fault in the region, extending more than 100 miles from the U.S.-Mexico border into the burgeoning inland desert east of Los Angeles.
“We expected there would be some increased chance of earthquakes on both the Elsinore and San Jacinto faults,” said geophysicist Eric Fielding of the NASA Jet Propulsion Laboratory.
Scientists are also keeping a close eye on the Elsinore fault, which branches into heavily populated Orange County and the Los Angeles metropolitan region. The Elsinore fault has not produced a major quake in more than a century.
The Easter quake, however, appeared to relieve stress on the San Andreas Fault — slightly reducing the chance of a quake on what has been one of California’s most notorious fault lines, Fielding said.
It’s not unusual for large earthquakes to unleash aftershocks and distant quakes for months and sometimes years. The 1992 magnitude-7.3 Landers quake that struck the Mojave Desert has produced some 10,000 aftershocks that continue today. Scientists said the Landers quake also triggered tremors in places up to 775 miles away.
Wednesday’s quake is considered a “triggered quake” and not an aftershock of the Baja shaker because it struck north of where scientists would expect aftershocks to occur, said seismologist Kate Hutton of the California Institute of Technology.
The difference is technical, largely due to the distance from the original quake, she said.
Laura Anderson, a manager at The Palms at Indian Head Hotel in Borrego Springs, said she ran outside when the shaking started Wednesday and was surprised to learn the temblor’s magnitude wasn’t higher.
“It was enough to knock over some wine bottles and some pictures fell off the wall,” Anderson said.
Police Lt. John Booth said there were no reports of serious damage or injuries in Palm Springs, a desert city of about 43,000, but the phone rang off the hook and many residents were shaken up by the largest quake they could remember.
Hutton said the fault rupture lasted about four or five seconds.
In the last 50 years, four other quakes larger than magnitude 5 have struck the San Jacinto fault zone. The last one occurred in June 2005.
U.S. Geological Survey: earthquake.usgs.gov/
Tags: Accidents, California, Deserts, Earth Science, Los Angeles, North America, Palm Springs, Seismology, United States