Today a new study was released in the journal Nature Communications that determined the causes of the unusual seismic activity (earthquakes) around Azle (northwest of Fort Worth) in November-December 2013, which Brantley Hargrove wrote about in the May 2014 issue of D Magazine.
Researchers from SMU, the University of Texas at Austin, and the U.S Geological Survey determined that activities related to oil and gas operations in the area, as the Morning News notes, are responsible for “shifting faults below Dallas-Fort Worth that have not budged in hundreds of millions of years”:
The scientists zeroed in on an unusual mechanism behind the quakes: workers pushing liquid into the ground on one side of a fault and sucking gas and groundwater from the other side of the fault.
“The combination of these activities seems to have triggered the earthquakes, and that was a real surprise to us,” said Matthew Hornbach, a geophysicist at SMU and a lead author of the paper.
Injecting fluids into the ground or extracting them has long been known to cause quakes, but rarely — if ever — have the two been caught acting in concert.
The geology of each region is unique, however, so these mechanisms may not be at work elsewhere.
So this isn’t evidence that the string of earthquakes over the last year that have been centered in Irving and parts of Dallas can also be blamed on the energy industry (research on those continues), but, c’mon. It is the third area of seismicity to be linked to pumping stuff into and out of the ground, and:
The seismologists also discounted natural shifts in tectonic plates as possible earthquake triggers. The two faults they mapped in Reno do not reach the surface, which suggests the faults have been dormant for more than 300 million years.
Yes, we shouldn’t ignore that the earthquakes haven’t continued near Azle, even as the wells are still operating. But what this study makes plain is that we don’t understand nearly as well as we should the consequences of injecting chemicals and wastewater deep beneath the surface. We are right to be highly skeptical when Exxon and XTO, plus the Railroad Commission (you know, the folks that are supposed to be regulating this business), tell us there’s nothing to worry about.