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Los Angeles and Earthquakes: Similar Areas Could Have More Double Earthquake Risk

Feb 10, 2016 05:56 PM EST
Images of double earthquakes in Pakistan, made with an interferogram
The chance of one earthquake connecting to one in a nearby fault and creating double earthquakes is higher than previously thought, says a new study. This could have impacts for Los Angeles, the front of the Himalayas, and other regions.
(Photo : UC Riverside)

Earthquakes have greater reach than previously thought. In fact, their ruptures can leap further -- a good bit further than previous research has known. This could have real repercussions for Los Angeles and other seismically active areas of the world.

That is, a study from the University of California Riverside, recently published in the journal Nature Geoscience, found that an earthquake that starts out on one thrust fault can move outward 10 times farther than previously believed, connecting to a nearby thrust fault, bringing about a much larger range for double earthquakes, also called earthquake doublets.

In multiple-thrust fault areas, such as Los Angeles, one earthquake could connect to another fault and double the impact.

The study authors, including Gareth Funning at UC Riverside, say that one such example is if one earthquake spread from the Puente Hills thrust fault under downtown Los Angeles, to the Sierra Madre thrust fault running near to Pasadena, according to a release.

Other areas with multiple thrust faults in near proximity are the Ventura, Calif. area; the Middle East, especially around Tehran, Iran; the front of the Himalayas, such as in Pakistan, India, Afghanistan and Nepal.

In studying a 1997 Pakistan earthquake, the researchers showed that it was two events: a magnitude 7.0 earthquake, then a magnitude 6.8 event that followed 19 seconds later and took place about 30 miles to the southeast.

The second quake was not an aftershock, says Funning -- because the events took place so near together in time and were similar in size. The many aftershocks that occurred were a good bit smaller.

Regarding Los Angeles, "This is another thing to worry about," Funning said. "The probability of this happening in Los Angeles is probably pretty low, but it doesn't mean it can't happen."

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

-Follow Catherine on Twitter @TreesWhales


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