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Aftershocks are possible up to five years after August 2011 Virginia earthquake

Posted at 10:35 AM, Jul 01, 2013
and last updated 2013-07-01 14:47:07-04

RICHMOND, Va. (WTVR) – Even though the aftershocks in central Virginia are fewer and farther between, and gradually less intense, one earthquake expert says we can continue to feel the tremors for up to five years after the initial Louisa County earthquake August 23, 2011.

Meteorologist Carrie Rose spoke with IRIS Consortium scientist Dr. John Taber while she was in Nashville, TN last week for the 41st Conference on Broadcast Meteorology/Second Conference on Weather Warnings and Communication. (CLICK HERE to see the official Twitter feed she managed from the conference.)

Taber gave a presentation about earthquakes, and Carrie asked him afterward some of the questions you have been asking ever since the initial earthquake near Mineral, VA. Here is her conversation with him:

Carrie also asked Taber if the 2011 earthquake was a “preview” of a bigger, near-future earthquake. Taber says, “not likely.” In fact, he says we probably will never experience an earthquake of that magnitude in our lifetime. It’s not impossible, but “the chances are very slim” in the Central Virginia Seismic Zone. Why? Because that earthquake, and the 84 subsequent “settling” aftershocks, have released the energy that had built up along those complex, folded and buried faults. The vast majority of the pressure was relieved on August 23, 2011. With that relieved pressure, tension in the Central Virginia Seismic Zone could take several lifetimes to rebuild. That seismic region is show in Taber’s presentation map below as a yellow bulls-eye. But we aren’t the only old fault region in the East U.S. The other yellow to red areas are also old faults that can, slowly over time, build up pressure and “reactive,” (i.e., cause an earthquake).

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Can we forecast future earthquakes in these old areas? Nope, says Taber. It’s not like forecasting atmospheric weather events. Think of earthquake “outlooks” like climate outlooks. Seismologists can look at fault regions to get a long-term idea of which ones are at risk of releasing the energy they are slowly building up.

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Another topic Taber covered was on hydraulic fracturing, also known as “fracking.” He says that recent research correlates fracking to a “man-caused” earthquake in Oklahoma. However, these types of earthquakes are usually small (around magnitude 2.0 or less) and rarely felt (except by direct neighbors to the work). But because of the concentration of fracking work in Oklahoma in recent decades, there does appear to be a solid link between the two.

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Taber also answered why we are registering more earthquakes over the past century. Is it because the earthquake activity itself is increasing or earthquakes are getting more intense? No and no. Because of better measuring equipment and sensors, we are better-able to both measure and quantify seismic activity globally.

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Wait, the Richter scale is gone?! In case you missed the memo, yes, we now refer to earthquakes based solely on their magnitude, not their Richter scale value. Here’s why:

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CLICK HERE to see when we had our last confirmed aftershock, and see the full list of aftershocks since August 2011.

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