FanPost

7/12/2012 OT 2



http://stateimpact.npr.org/texas/2012/07/12/why-earthquakes-are-shaking-north-texas/

Yet another earthquake has rattled North Texas. Early Tuesday morning, the city of Keene, 25 miles south of Fort Worth, experienced what the U.S. Geological Survey says was a 2.4 magnitude earthquake.

Earthquake events have been on the rise in an area that hasn’t really seen a whole lot of quakes in the past. That was before disposal wells were constructed nearby, used to dispose of wastewater from hydraulic fracturing, or “fracking.” (For an in-depth look at disposal wells, check out this report from ProPublica.)

“We’ve been looking at the question of whether the number of earthquakes occurring across the mid-continent has changed in recent years. And we find that there is a statistically significant increase in the rate just over the past several years. And many of these are in areas where we know there is a lot of energy activity,” U.S. Geological Survey geophysicist Bill Ellsworth tells StateImpact Texas.

In less than a month, the Johnson County area has been shaken by at least seven different quake events.

ing Cause Earthquakes?

Blogger Sharon Wilson, an opponent of fracking, chronicled the tremors recently on her site. All of the data comes from the US Geological Survey, which we double-checked. Each link will take you to the Survey’s event page for the quake:

And if you compare the location of disposal wells and earthquake events, you’ll find an interesting pattern. The two maps appear to match up. Here’s a map of disposal wells in the area:

MAP COURTESY OF FRACFOCUS.ORG

A map of the hydraulic fracturing disposal wells in North Texas.

And here’s a map of the recent quakes in the area:

MAP COURTESY OF EARTHQUAKETRACK.COM

A map showing the recent outbreak of earthquakes in North Texas.

Ellsworth claims that the experience in North Texas parallels that of a California geothermal field called The Geysers, just north of San Francisco. An explosion of industrial activity there has been responsible for more than a thousand earthquake events every year. Most of the quakes haven’t surpassed a 2.0 magnitude. Generally, an earthquake magnitude of 4.0 or larger is considered to be destructive. But Ellsworth says that “there’s always the possibility that something larger might occur.”

Similar clusters of earthquakes near injection well sites have been reported in central Arkansas, Oklahoma, and along the New Mexico-Colorado border.

But unlike naturally earthquake-prone sites like California, states like Texas might not be ready for the bigger quakes.

“In California or on the West Coast, we have very high building standards for earthquake safety. As we move away from the active tectonic margins, those building code standards are relaxed because there’s less of a threat. So, buildings in many parts of the central part of the country will be more vulnerable to the same earthquake compared to if that earthquake were to happen in an area such as California, Nevada, or Washington,” says Ellsworth.

While scientists and public officials alike work to study the link between disposal wells and induced earthquakes, citizens can and should take steps to prepare themselves, says Ellsworth.

The U.S. Geological Survey recommends a 7-step plan to manage risk and respond to an earthquake event. You can learn more about this by reading the USGS guide to earthquakes, Putting Down Roots in Earthquake Country.

You can also learn more about the link between hydraulic fracturing disposal wells and earthquake events by reading our explainer: Does Fracking Cause Earthquakes?

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