HISTORY AND RESPONSE TO INDUCED SEISMICITY IN ARKANSAS WITH EXAMPLES OF PREVIOUS CASE STUDIES... WHAT WE HAVE LEARNED?

North-central Arkansas has seen a significant increase in both unconventional resource development and seismicity in an area known as the Fayetteville Shale Play since 2009. Though the area is historically seismically active (Enola earthquake swarm of 1982), this increase in seismic activity since 2009 is likely a combination of both natural and human-induced clusters and even swarms of earthquakes. There have been three published cases of potentially induced seismicity in Arkansas. Horton (2012) proposed that a hydraulic connection existed between the injection depths at two salt-water disposal wells (SWDs) and the nearby Guy-Greenbrier fault, a previously unknown fault in north-central Arkansas illuminated by over 1,300 earthquakes (M≤4.7) that occurred from August of 2010 to December of 2011 (known as the Guy-Greenbrier earthquake swarm of 2010-2012). The regulatory response which resulted from this earthquake swarm included commissioning a six month study by the Arkansas Geological Survey (AGS) and the Center for Earthquake Research and Information at the University of Memphis (CERI) to determine potential causality, changes to the permitting rules for SWDs, and a moratorium of SWDs over a large area of the play. Other published cases include: Horton and Ausbrooks (2010 and 2011) suggested that earthquakes (M≤3.0) that occurred from October of 2009 to January of 2010 near Greenbrier, Arkansas were related to a nearby SWD. Cox (1991) suggested a potential relationship of earthquakes with injection/disposal wells associated with brine production in south Arkansas.