Just as the Dallas City Council shot down an energy company's plans to drill for gas in the city limits, a new study raises further questions about the role energy exploration plays in small earthquakes shaking up Texas.
Earlier research has linked quakes to the disposal of fracking fluid. So Cliff Frohlich, a scientist at UT's Institute for Geophysics, examined two years of seismic activity in South Texas, home to the Eagle Ford shale. He found something different -- that pulling shale oil out of the ground is responsible for both minor quakes in South Texas and bigger quakes, such as the magnitude 4.8 Fisher earthquake in 2011.
The study, which will be published in the journal Earth and Planetary Science Letters, adds to the pile of research suggesting that pulling stuff out from deep underground in populated areas comes with risks.
"It has long been known that earthquakes can be induced by extraction of fluids from underground," says William L. Ellsworth, a researcher at the US Geological Survey who isn't involved with this study. "This includes not only oil, but also gas, steam (from geothermal reservoirs) and water."
But while Frohlich's research further confirms that extracting oil from underground causes quakes, he says he found no link when he looked at injection sites, the places where natural gas companies dump their fracking fluid underground.
"It looks like in the Eagle Ford, it's the removal of material that is causing earthquakes, not the injecting of material," he tells Unfair Park.
In response to the research, The Atlantic magazine put on its science glasses and concluded "this report does seem like a bit of good news for the oil and gas industry."
The Wall Street Journal, meanwhile, made a subtle jab at "environmental and community groups" that have "expressed concerns about a link between earthquakes and hydraulic fracturing." The newspaper concluded that "the new study doesn't find much evidence that the man-made fracturing is causing earthquakes all by itself."
"Active fracking hasn't been linked to large induced earthquakes very frequently," says Nicholas van der Elst, a researcher at Columbia University who recently linked injection wells with earthquakes in Snyder, Texas in a study of his own. "The real concern with fracking is the long term disposal of the fracking fluid once the frack job is done."
And Frohlich, the researcher who authored the latest study, has also found links between those disposal sites and earthquakes -- just not in this particular study. In a 2012 study, Frohlich found that most earthquakes in the Barnett Shale region of North Texas occur within a few miles of injection wells.
So why would injection wells cause earthquakes in North Texas but not South Texas? Frohlich says that the two areas are different geologically, and the Eagle Ford shale has been drilled for much longer.
"The Eagle Ford in the Edwards [area] is an area where they've been producing since the 1970s," he says, "whereas Barnett they just started fracturing since 2004."
Researchers still don't know how many of the earthquakes caused by man-made messing with the ground are dangerous and how many are harmless little shakes. Van der Elst says more research needs to be done, and Frohlich, for his part, doesn't think people should be "hugely concerned." But in an interview with FuelFix, Frohlich added that "some of the earthquakes like the 4.8 in Fashing are getting large enough to be of concern. If that had happened in an urban area there would have been severe damage."
