UNDERSTANDING RECENT NORTH TEXAS EARTHQUAKES
Scientific investigations of earthquake clusters are being conducted
by seismologists from SMU’s Huffington Department of Earth Sciences in Dedman College
A recent series of earthquakes near the site of the old Cowboys Stadium in Irving are renewing scientific questions about the nature of these events and heightened local and national concerns about the impact of activities related to shale gas production on geological infrastructure and subsurface structures.
The Irving earthquakes are the latest in a series of four clusters that have hit the North Texas area since 2008. The first group hit near DFW International Airport between October 30, 2008, and May 16, 2009. It was followed by a series of quakes in Cleburne between June 2009 and June 2010 and a third series in the Reno-Azle area between November 2013 and January 2014.
The SMU seismology team includes Prof. Brian Stump, SMU’s Albritton Chair of Geological Sciences, Heather DeShon, associate professor of geophysics, Beatrice Magnani, associate professor of geophysics, and Matt Hornbach, associate professor of geophysics, as well as Chris Hayward, research scientist.
SMU seismologists say more than 120 earthquakes have been reported in the North Texas area since 2008. Prior to 2008, a felt earthquake had not been reported in the North Texas area since 1950. Peer-reviewed publications have been issued by the SMU team on the Cleburne and DFW clusters, and another is pending on the Reno-Azle cluster.
If a member of the public feels an earthquake, he or she is asked to report it to the U.S. Geological Survey "Did You Feel It?" site.
"I think the more important thing for people in the Dallas-Fort Worth area to remember is that since we don't have a lot of seismic stations, it is incredibly important when you feel an earthquake to report it to the U. S. Geological Survey," DeShon said. "This is very valuable information to us. It helps us to really understand how the ground moved and how it accelerated over the metropolitan area."
While all North Texas events
to date have been small (less than magnitude 4) and at a depth of about three miles, seismologists are unable
to determine the potential maximum magnitude magnitude for the region. Rapid deployment of seismographs to locate events is done to characterize subsurface faults and help define the hazard. For the Irving cluster, scientists at SMU have installed and are operating a seismic network to acquire data that may be used to determine the location and possible cause of the earthquakes.
“It’s premature to speculate on the cause of this current series of seismic events,” said Brian Stump, SMU’s Albritton Chair of Geological Sciences. “We’re just getting started. We want to support the local community in understanding these earthquakes, and the team appreciates the cooperation of the City of Irving, the United States Geological Survey and IRIS in helping us get the best information possible.”
The primary research goal will be to conduct the data analysis needed to improve identification of earthquake location and characterize the size, mechanisms and quantify the maximum ground accelerations associated with the events. The improved network geometry and closer stations will make it possible to more accurately locate the events and thus improve the imaging of the associated fault. This information will allow SMU scientists to estimate the size and nature of any fault(s), which can provide insight into the maximum size of the earthquake(s) they may produce. SMU also will be able to measure peak-ground-accelerations, which are needed to better estimate hazards.
Finally, the spatial relation of the felt earthquakes to fluid injection points related to shale gas development in Texas and other states remains an open question. Understanding if and/or how injection of fluids into the crystalline crust reactivates otherwise inactive faults has important implications for seismology, the energy industry, and society. The number and diversity of instruments SMU has deployed is unique and provides an unprecedented opportunity to make progress on this topic.
Instrumentation has been provided in part by the U.S. Geological Survey and the Incorporated Research Institutions for Seismology (IRIS). The ability to deploy the stations has been supported by both individuals and local communities in the area. All waveform data collected by SMU is publically available, archived at the IRIS Data Management Center.
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