Earthquake In South Texas: Fracking Fluid at Fault?

Oct 20, 2011

A 4.8 magnitude earthquake struck an area of South Texas today that is a center point for natural gas and oil production in the Eagle Ford Shale. The quake’s epicenter was here in the unincorporated community of Campbellton in Atascosa County near Karnes County. You can see numerous wells in the county in this map from the Texas Railroad Commission. (Note: An earlier version of this story incorrectly placed the epicenter in Karnes County.)

A University of Texas seismologist says hydraulic fracturing itself does not cause earthquakes. But he says earthquakes have been associated with the disposal of fracking fluids.

 “They [drilling companies] pump the water back into the ground into a deep aquifer to get rid of it,” earthquake researcher Cliff Frohlich at UT’s Institute for Geophysics told KUT News.  

“The quakes have been associated with the pumping of water back into the ground, not the producing of the gas,” he said, pointing to seismic activity in North Texas and in Arkansas.

In September, Arkansas banned the use of deep wells to store waste water. StateImpact Pennsylvania points to a study by Southern Methodist University and UT that linked small earthquakes in the North Texas Barnett Shale with the practice, and says the Army Corps of Engineers has expressed concern about drilling for natural gas near dams. 

But Frohlich says it’s too soon to say if waste water disposal activities were related to today’s 4.6 magnitude quake in South Texas.  “That’s a question,” he said.

The area southeast of San Antonio has felt earthquakes before. There was a 4.3 magnitude earthquake in 1993 near the same location, and there have been smaller quakes recorded back to the 1970s, Frohlich said.