Researchers at Southern Methodist University have linked a string of 2009 and 2010 earthquakes in Texas to the injection of fracking wastewater into the ground, according to a new study.
The researchers examined the group of more than 50 earthquakes that hit the area of Cleburne, Texas in 2009 and 2010, and found that they could have happened because of wastewater injection wells associated with fracking operations. Before 2008, the Fort Worth Basin of Texas had never experienced an earthquake.
“Because there were no known previous earthquakes, and the located events were close to the two injection wells and near the injection depth, the possibility exists that earthquakes may be related to fluid injection,” the authors write in their report.
In Cleburn, injections of fracking wastewater began in 2005, but earthquakes didn’t start until 2009. This doesn’t rule out the potential for wastewater injection to have caused the quakes, however — scientists believe the fracking process makes it more likely in general that an earthquake will happen, even if there is a delay.
“The model I use is called the air hockey table model,” Cliff Frohlich, a research scientist at the Institute for Geophysics at the University of Texas at Austin, told StateImpact Texas. “You have an air hockey table, suppose you tilt it, if there’s no air on, the puck will just sit there. Gravity wants it to move but it doesn’t because there friction [with the table surface].”
Once the air is turned on, the puck slips — the same way, he says, if you pump wastewater into a fault, the fault can slip and cause an earthquake. The presence of the fluid could make it much easier for an earthquake to happen, even years later when an external force becomes strong enough to move the earth. Brian Stump, chairman of Geological Sciences at SMU, said he thinks an earthquake can only be triggered if the fluid reaches an underground fault.
In general, linking wastewater injection to earthquakes isn’t uncommon (wastewater injection has been confirmed as a possible trigger of earthquakes by the U.S. Geological Survey). In 2010, researchers from SMU and UT-Austin determined that a wastewater injection well was a “plausible cause” for the series of earthquakes in North Texas in 2008 and 2009. Earlier this year in Ohio, fracking wastewater disposal was also linked to the 109 earthquakes that shook Youngstown in 2011 — an area that hadn’t ever experienced an earthquake before an injection well came online in December 2010. After a 3.9-magnitude earthquake struck the Ohio city on Dec. 31, 2011, the injection well was shut down.
This also probably isn’t the last time we’ll hear about the link between wastewater injection and earthquakes in Texas in particular. Last month, North Texas was hit by more than 20 earthquakes, prompting calls for an investigation into a possible wastewater disposal link.
“If it is determined that quakes are caused by the disposal wells, then the disposal wells need to stop. It’s that simple,” the city of Azle’s Mayor Alan Brundrett said.