Spooked by a series of earthquakes since November, hundreds of people at a town hall meeting Thursday evening let state officials know they are frustrated about the absence of explanations for the outbreak.
They were still frustrated when they went home.
At times the meeting, while generally orderly, turned raucous as participants yelled out support for a homeowner’s story or hooted when railroad commission representatives said they don’t know what is causing the unusual seismic activity on the western edge of the Metroplex.
Most of the speakers had their own idea about the cause: natural gas production in the Barnett Shale that underlies much of the western Metroplex.
“Something is going on. Stop drilling and see what happens,” said Victoria Ball of Azle, a recommendation that drew applause and cheers from the audience.
About 30 relatively small earthquakes have been recorded in the Azle area in the past two months, the most recent on Dec. 23. That one was near Reno, a community northwest of Azle, and measured a magnitude of 3.3, according to the U.S. Geological Survey.
No major damage or injuries have been reported, but speakers Thursday night recounted damage to their homes, broken water pipes and disrupted sleep.
Although scientists have not generally associated drilling and hydraulic fracturing with reported earthquakes, considerable research links seismic events to injection wells, which dispose of millions of gallons of wastewater deep under ground.
The meeting in the auditorium of Azle High School was organized by Texas Railroad Commissioner David Porter. The state agency regulates the oil and gas industry, and its staff is studying the issue, Porter said.
“I understand it got a little contentious at times,” Porter said as the meeting came to a close. “I want to let you know we were here to listen tonight,” he said.
Porter promised that “we’re in the process of trying to get some state research done” to find the cause of the swarm of quakes.
Reno Mayor Lynda Stokes, who was among the speakers, said that as a public official she sympathized with her Austin counterparts’ inability to offer precise answers.
But, she said, the state needs to do much more than just listen to complaints.
“People want to know why,” she said.
Frances Kulas of Reno said the first earthquake she experienced “sounded like a helicopter landing on our home, and then ‘boom.’ Nothing fell off the walls, but now our doors stick, and they didn’t do that before,” Kulas said.
“I do believe the injection wells are causing the majority of it.”
Ed Ireland, director of the Barnett Shale Energy Education Council, an industry group, said in an interview that the link between earthquakes with injection wells is not conclusive. Ireland attended the meeting but did not speak.
It appeared that almost everyone in the audience of nearly 1,000 had been exposed to the quakes. For example, when speaker Gale Wood asked how many people had heard the sonic boom-like rumble accompanying the quakes, nearly everyone in the audience raised a hand.
Stokes, the Reno mayor, said she hasn’t gotten many updates on the state’s efforts, “but I expected to now,” given the frustration evident at Thursday’s meeting.
In December, scientists at Southern Methodist University deployed four seismic monitors provided by the USGS to collect data focusing on a 5-to-6-mile stretch near Azle and Reno to the northwest. The researchers will use 15 other sensors in a wider area and expect to take several months to complete their study, depending on the amount of seismic activity.
In 2008 and 2009, there was an outbreak of small quakes near Dallas-Fort Worth Airport. A seismic study by SMU and UT-Austin researchers identified a small injection well in the area as what it called the “plausible cause” of the quakes. The quakes ended after the injection well stopped operating in August 2009.
Cliff Frohlich, associate director of the Institute for Geophysics at the University of Texas at Austin and a participant in the DFW Airport study, said establishing an absolute link between a particular injection wells and an earthquake is difficult.
“It depends on the level of confidence you want in the results,” he said Thursday in an interview before the Azle meeting.
In a separate 2012 study, he found that while not all injection wells were linked to earthquakes, “injection-triggered earthquakes are more common than is generally recognized.”
That study, like the current SMU research, placed temporary seismographic monitors in the Barnett Shale to chart small seismic events and compare them with the location and size of injection wells.
The additional seismic monitors in the Azle area will allow scientists to more accurately pinpoint the epicenter of small quakes, Frohlich said. There are about a dozen permanent seismographic measuring stations around the state, he said, and the estimated epicenter of a small quake could be off the actual location by five or 10 miles, depending on where it occurs.
Data from USGS monitors in the area and elsewhere in Texas and the nation can be viewed online at http://earthquake.usgs.gov/monitoring/netquakes/map/s/map/