SMU seismologists investigate cause of North Texas earthquakes

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A researcher sets up an instrument to analyze the local earthquakes. (Courtesy of Hillsman Jackson)

 

The Reno-Azle area, west of Fort Worth, has been experiencing more than 30 earthquakes since November, according to the U.S. Geological Survey.

The largest earthquake was 3.7 on the Richter scale. The majority of the earthquakes are at a low magnitude.

“The real question is how big can these earthquakes get,” said Christopher Hayward, director of geophysics research at SMU.

A group of 12 SMU scientists and students, a well as a Lake Highlands High School intern, are currently studying the Reno-Azle area.

Associate geophysics professor Heather DeShon is leading the study and Hayward is leading the installation process. The group has installed 12 instruments so far.

Questions whether the earthquakes are occurring because of fracking by oil and gas companies lead a group of Azle, Texas residents to travel to the state capitol Jan. 23.

“It is important we do not rush to conclusions,” DeShon said at a press conference Friday. “I understand people want results quickly. But we have to sit and wait a little while.”

Fracking is the injection of water, sand and chemicals under high pressure into bedrock to increase the flow of oil or gas. Of the about 35,000 shale gas wells in the U.S., only two cases show fracking-induced seismicity.

According to Hayward, the wastewater injection wells are more of a concern. Wastewater injection wells, about 30,000 in the U.S., dispose of waste fluids from producing oil and gas wells by injection wells drilled below fresh water aquifers. According to Induced Seismicity Potential in Energy Technologies, there were eight case studies linking earthquakes to these wastewater wells in the U.S. in 2011.

Wastewater disposal is a separate process from the fracking operation and may occur away from the fracked well.

In December 2013, four digital monitors provided by the USGS were deployed to monitor the seismicity in the area. The research team is deploying several single channel sensors provided by the Incorporated Research Institutions for Seismology (IRIS) Program.

Rotating teams of two install the instruments in a variety of places from schools to private homes in the area that are near power and internet connections.

What is this?

“They [residents] are allowing us to install; they’ve been very nice, very cooperating,” Hayward said. “We are very appreciative of them.”

The instruments are highly sensitive, picking up even the energy from footsteps. They are placed within the epicenter of the events and within 25 kilometers of the events. Scientists will then cross analyze the data to improve our understanding of the earthquake locations, size, fault plane solutions, accelerations associated with the events.

Once the instruments have all been deployed the team will no longer travel to the area.

The seismic activity in the Reno-Azle area is similar to activity that occurred around Cleburne, Texas and the Dallas/Fort-Worth International Airport between 2008 and 2011.

At DFW, the injection well began operating before the earthquakes began and that the earthquakes were close to the well. In the case of the Cleburne area, there was not a strong timing relationship between the earthquakes and the wells.

Heyward and SMU seismology professor Brian Stump, along with other SMU and University of Texas at Austin scientists, were part of that study as well.

The difference between the DFW/Cleburne studies and the Reno-Azle studies is the technology available to scientists.

“We can do a bigger and better job at looking at the data,” Stump said. “A lot more details in understanding of the cause in the earthquakes.”

In both studies, rather than information being directly sent back to campus, the instruments were left on site for several months, then seismologists would return and download the data to their laptop to analyze it.

The educational website has been set up with information about where the instruments are installed, frequently asked questions and photos.

 

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