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Proceedings of the National Academy of Sciences

Frequency of fluid injection-triggered earthquakes

Earthquakes triggered by injecting fluids deep underground may be more common than previously recognized, according to a study. Researchers have long known that fluid-injection operations-used in the production of geothermal power, extraction of petroleum, and disposal of fluid wastes-can cause earthquakes on rare occasions, but it is unclear why some injection wells induce earthquakes whereas others do not. Cliff Frohlich analyzed seismic activity in the Barnett Shale of northern Texas between November 2009 and September 2011 and compared the properties of injection wells located near earthquake epicenters. The author identified the epicenters for 67 earthquakes-more than eight times as many as previously reported by the National Earthquake Information Center-with magnitudes of 3.0 or less. The majority of the quakes were located within a few kilometers of one or more injection wells, and one-third of the quakes clustered into eight geographic regions. All of the wells nearest the epicenters within these eight regions reported high rates of injection, exceeding 150,000 barrels of water per month. However, the Barnett Shale hosts more than 100 wells with similar injection rates that experienced no nearby identifiable earthquakes during the study period. The author posits that fluid injection may only trigger earthquakes if fluids reach and relieve friction on a nearby fault.

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Article #12-07728: "A two-year survey comparing earthquake activity and injection well locations in the Barnett Shale, Texas," by Cliff Frohlich

MEDIA CONTACT: Cliff Frohlich, Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX; tel: 512-471-0460 (office, until August 15), 512-467-9897 (home, until August 15), 858-361-5588 (home, August 15-20), and 512-633-1763 (mobile, August 15-20); e-mail: cliff@ig.utexas.edu



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