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Data Lacking for Human-Caused Earthquake Studies

The most comprehensive analysis to date of a series of earthquakes that included a 4.8 magnitude event in East Texas in 2012 has found it plausible that the earthquakes were caused by wastewater injection. The findings also underscore the difficulty of conclusively tying specific earthquakes to human activity using currently available subsurface data.

The study, conducted by the Bureau of Economic Geology, was published April 13, 2016, in the Journal of Geophysical Research: Solid Earth.

The researchers built the first computer model for this site that simulates the effects of fluid injection on the stability of the fault that potentially generated the earthquakes. In theirsimulations, researchers used a range of likely values for input parameters, including physical properties of the reservoir and the orientation of the fault. Earthquakes were generated using a certain range of input parameters, but no earthquakes were generated using a wider set of equally probable parameters.

The 4.8 magnitude earthquake occurred on May 17, 2012. It was the largest ever recorded in the area and followed a series of smaller earthquakes that started in April 2008, some 17 months after two wastewater injection wells began operating nearby.

The researchers tested a number of likely scenarios to assess if the volume and rate of fluid injected into the disposal wells were high enough to cause nearby faults to slip. This is the first study to simulate the mechanics of an earthquake generated by water injection for this site.

“It is part of a continuing research effort by The University of Texas at Austin,” said Peter Eichhubl, a bureau senior research scientist. “We used a more rigorous approach than previous studies, but our analyses are limited by the availability of robust, high-quality data sets. This study demonstrates the need for more and higher-quality subsurface data.”

Bureau researchers Zhiqiang Fan and Julia Gale co-authored the report. Funding was provided through the Ultra-Deepwater and Unconventional Natural Gas and Other Petroleum Resources Research and Development Program.