Those who live in and around Dallas/Fort Worth are probably aware that there were a series of small earthquakes in Irving, Texas – a city west of Dallas and east of Fort Worth – on Jan. 6, 2015. Most of the quakes were small, and they mainly centered just east of where the old Dallas Cowboys stadium (Texas Stadium) was located in Irving (the stadium was demolished in April 2010); however, two quakes, a 3.5 and a 3.6 on the Richter scale, were definitely large enough to be felt miles away.
News stations were quick to report that oil and gas activity in Irving, specifically hydraulic fracturing, was responsible for the seismic activity. While Irving is located on the Barnett Shale, there isn’t actually any drilling or hydraulic fracturing taking place anywhere near the center of the earthquakes. There is one existing natural gas well about two miles from the quakes’ center, but it was drilled in 2009 and was shut-in (closed down) in 2012 and has been inactive since. The closest well being drilled is at least 20 miles away, in Arlington.
It is also important to note that scientists, including geophysicists and seismologists, report an extremely low risk of hydraulic fracturing causing seismic activity that can be felt by humans. Dr. Cliff Frohlich, senior research scientist at the University of Texas at Austin’s Institute for Geophysics, conducted a definitive survey between 2009 and 2011 concerning Barnett Shale injection wells and earthquakes, published in 2012. Injection wells, or saltwater disposal wells, dispose of hydraulic fracturing wastewater deep underground. Dr. Frohlich found that some saltwater disposal wells induced small (too weak for humans to feel) earthquakes in their vicinity, but that most did not. He concluded that saltwater disposal wells, if drilled on or near a fault, could induce small seismic events under certain circumstances.
In the case of Irving, there aren’t any saltwater disposal wells near the location of the earthquake activity. A more likely explanation for the January earthquakes could be due to a natural cause, the Balcones Fault Zone – a set of faults running from Southwest Texas up through north Texas, which has produced small earthquakes for many years.