Wednesday, October 21, 2015


Scientists have been saying for a while that it's not a matter of if but when the so-called Big One will strike Southern California. A worst-case scenario has a 7.8 on the San Andreas fault impacting Los Angeles someday and killing as many as 1,800 people, according to experts.

But what about a not-so Big One? 

A new study from the NASA's Jet Propulsion Laboratory near Pasadena predicts that a magnitude 5.0 or greater earthquake will hit the Los Angeles basin within two and a half years. The paper was published in the journal Earth and Space Sciences. JPL officials have reportedly declined to reveal the full document to the press.  

Overnight the U.S. Geological Survey cast doubt on the prediction.

It noted in a statement that the "random" chance of such a temblor hitting L.A. in three years was very high anyway.

"The accepted random chance of a M5 [magnitude 5] or greater in this area in 3 years is 85 percent, independent of the analysis in this paper," the USGS said.

The JPL research "has not yet been examined by the long-established committees that evaluate earthquake forecasts and predictions made by scientists," the agency added. "The lack of details on the method of analysis makes a critical assessment of this approach very difficult."

JPL seismologists measured energy released and strain that remains following local earthquakes, focusing most specifically the La Habra temblor of March 28, 2014.

They discovered an energy "deficit" that "must eventually be filled with large earthquakes," according to an abstract of the study, which is titled "Potential for a large earthquake near Los Angeles inferred from the 2014 La Habra earthquake."

While a magnitude 5 or greater rocker is essentially going to happen in the next three years, the JPL scientists say, the quake forecast here could actually be as great as a 6.3, they said.

"Significant ground deformation and infrastructure damage can occur beyond the epicentral region of a moderate earthquake near Los Angeles," the abstract says.

We're not entirely sure what this means, except that it's not good.
The JPL scientists say that a 6.1 would release 81 percent of pent up energy or "strain." A 6.3 would release 100 percent of it, the scientists said.

"The observed ground deformation could represent release of accumulated tectonic strain," the abstract says. 

The 5.1 temblor on the Puente Hills fault last year hit hardest in north Orange County, essentially its origin. Gas lines were ruptured, buildings sustained minor damage, and two people were injured in a rollover vehicle crash likely caused by a quake-triggered rock slide.
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