August 22, 2010
LA ‘Big One’ May Hit Sooner Than Thought
In a US study, researchers said that strong earthquakes recorded along the San Andreas fault in southern California are more frequent than previously believed, and they fear the "Big One" could be just around the corner.
Scientists at the University of California at Irvine and Arizona State University examined geological records stretching back 700 years along the fault line about 100 miles northwest of Los Angeles.
They found that strong earthquakes -- 6.5 to 7.9 magnitude -- occurred every 45 to 145 years, instead of the originally established 250 to 400 years.
Since the last strong 7.9 magnitude earthquake that struck southern California in 1857, scientists believe the next "Big One" could happen anytime.
Scientists provided a summary of the research, which will be published in the September 1 issue of Geology magazine.
"What we know is for the last 700 years, earthquakes on the southern San Andreas fault have been much more frequent than everyone thought," said Sinan Akciz, the study's lead author.
A major earthquake in southern California, with an estimated regional population of 37 million, could kill tens of thousands of people and cause billions of dollars in damage, scientists predict.
UCI seismologist Lisa Grant Ludwig, chief investigator in the study, said people in the region should already be taking precautions.
Ludwig said its like watching storm clouds gather on the horizon. "Does that mean it's definitely going to rain? No, but when you have that many clouds, you think, I'm going to take my umbrella with me today."
"That's what this research does: It gives us a chance to prepare," she said.
Individuals should make sure they have ample water and other supplies on hand, safeguarding possessions in advance, and creating and testing family emergency plans. Authorities and officials should advocate new policies requiring earthquake risk signs on unsafe buildings and forcing inspections in home-sale transactions to disclose risk, said Ludwig.
Some things, she added, remain unpredictable. The highway grid, especially in Los Angeles, which even on the best day can be hopelessly gridlocked.
The data from the study shows that state residents and policymakers need to be well prepared, Ludwig told AFP.
Study co-author Ramon Arrowsmith, a geology professor at Arizona State, was more optimistic. "While earthquakes may be more frequent, they may also be smaller (starting at 6.5 magnitude). That's a bit of good news to offset the bad."
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