The U.S. Geological Survey may know within two months whether the earthquakes around Azle, Texas, can be linked to natural gas drilling activity.
USGS and researchers from Southern Methodist University have set up instruments to monitor earthquakes around Azle, about 20 miles northwest of Fort Worth. Residents and local officials suspect there's a link between a string of quakes and the disposal wells used to get rid of wastewater from natural gas drilling and hydraulic fracturing.
"We know the earthquakes are within a few kilometers of wastewater wells that are fairly high-volume wells," Art McGarr, a researcher with USGS, said in an interview Tuesday.
"We don't know whether there's a direct connection. With some analysis, we should be able to determine this within a month or two," he said.
A clear determination about the cause could put pressure on Texas regulators. The Texas Railroad Commission, which overseas oil and gas production in the state, has questioned the evidence linking underground injection and earthquakes.
Ramona Nye, a spokeswoman for the commission, said in an email, "Our staff will review any findings made by USGS."
That's a contrast from Ohio, where the state brought in researchers from Columbia University's Lamont-Doherty Earth Observatory to investigate a string of earthquakes in 2011.
Lamont-Doherty seismologist John Armbruster drove to Ohio and installed four seismic instruments on Dec. 1, 2011, with the help of a student. On Dec. 24, there was a magnitude-2.7 earthquake that was strong enough to be felt. Information from that quake showed it was centered within a half-mile of the bottom of the injection well.
State officials asked the owner of the well to suspend operations on Dec. 30, a day after the researchers presented their findings, according to a report on the earthquakes.
Armbruster said results from the Dec. 24 quake showed the odds were strong that the quakes were related to the well.
"It's not Powerball odds, but it's lottery odds," Armbruster said. "To us, it was a pretty good case."
Still, Youngstown had one more earthquake, a magnitude 3.9 on New Year's Eve 2011. That quake got national attention.
Armbruster said he and other scientists were convinced by then that the quakes were caused by the injection well. State officials announced their conclusion that it was related in March, along with new rules for injection wells. Companies have to survey for faults before they can get a state permit for a new injection well, and they have to use continuous pressure monitors and automatic shutoff equipment.
"When developing the rules, Ohio did not look to assign blame or find an immediate answer," Mark Bruce, a spokesman for the Ohio Department of Natural Resources, wrote in an email. "Gov. John Kasich took steps through the executive order to protect human health and safety, then ODNR crafted rules that gave us the necessary tools to better monitor, evaluate and understand seismicity."
Lamont-Doherty researcher Won-Young Kim later determined earthquakes that were too small to feel started shortly after the well started operations in December 2010. And there were as many as three a day, correlated with the injection volumes.
"That's Powerball odds," Armbruster said.
Azle, which sits over the Barnett Shale natural gas field, has had more than 20 small earthquakes since early November 2013. The largest have been a pair that measured magnitude 3.6, on Nov. 20 and Dec. 8.
No injuries have been reported, but about 850 residents confronted state officials during a Jan. 2 meeting to discuss the quakes. Many of them were concerned about the impact on their property values and said the commission was dragging its feet (EnergyWire, Jan. 3).
"I hope the government study will be different," Lynda Stokes, mayor of the neighboring town of Reno, said in an interview.
There are at least three injection wells near Azle. Up to now, state inspectors have checked only to see if the wells comply with Texas rules -- which don't address earthquakes.
The Texas Railroad Commission said Tuesday it will start a nationwide search to hire an in-house seismologist, whose job will be to conduct original research and coordinate other scientists (EnergyWire, Jan. 8).
Azle Mayor Alan Brundrett said hiring a seismologist was a step in the right direction, although a nationwide search could lead to delays.
"Hopefully, they will be able to have the seismologist in place by the time the USGS study is completed," Brundrett said in an email.