8.6 earthquake possible in Southern California? Caltech study suggests new ‘mega-earthquake’ risk

July 26, 2012 – LOS ANGELES – In recent years, scientists, first responders and utilities have been preparing for “The Big One,” that inevitable quake that will rock Southern California to its core. It’s coming. For sure. They just don’t know when. But the U.S. Geological Survey and Caltech have been on the ball, working from a likely scenario, a simulated “Shakeout” that would have a 7.8 quake hitting greater L.A. It would be deadly, destructive and put us in the dark for days, if not weeks. Unfortunately, a 7.8 might now be too low of an estimate for The Big One: Caltech researchers looked at Sumatra’s (April 11) 8.6 earthquake and concluded — maybe — that a similar temblor could happen along the same San Andreas fault that will produce our Big One. Make that a possible Bigger One. Scientists said the Indonesian rocker was larger than they ever thought such a quake “could be,” according to Caltech. It was a ‘intraplate strike-slip quake,” similar to what would happen at San Andreas, where much of California, from Baja to San Francisco, is moving north as the rest of America moves south. In Sumatra, scientists found that this was not only the biggest strike-slip fault temblor ever, but that it set of a series of right-angle ruptures that amplified the shaking, like a block of ice cracking up in the heat. And yes, it could happen here. The research, published last week in the journal Science Express, argues: The new details provide fresh insights into the possibility of ruptures involving multiple faults occurring elsewhere–something that could be important for earthquake-hazard assessment along California’s San Andreas fault, which itself is made up of many different segments and is intersected by a number of other faults at right angles. Lingsen Meng, lead author of the Caltech research: If other earthquake ruptures are able to go this deep or to connect as many fault segments as this earthquake did, they might also be very large and cause significant damage. The USGS, of course, is begging Southern Californians to prepare for our “mega-earthquake,” as academics called the Indonesian shaker. You know, flashlights, batteries, radios, water, nonperishable food. All that good stuff. –LA Weekly

contribution Rhonda