Mid-Continent Section

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Characterization and Classification of Discrete Clusters of Earthquakes from 2008–2015 in North-Central Arkansas, Natural or Induced: Illustrating their influence on the National Seismic Hazard Maps


North-central Arkansas has seen a significant increase in both unconventional resource development within the Fayetteville Shale Play and seismicity since 2009. The study area is historically seismically active, but it has seen an increase in seismic activity since 2009 that is likely a combination of both natural and human-induced clusters and even swarms of earthquakes (including the Guy-Greenbrier earthquake swarm of 2010–2011). We review earthquake catalogs from the Center of Earthquake Research and Information (CERI) and the Arkansas Geological Survey (AGS) to obtain key characteristics including location, magnitude, and depth of the earthquakes within each discrete cluster. Then we determine if a spatial and temporal correlation existed between discrete individual clusters of earthquakes that had occurred within 10km of an active Class II saltwater disposal well (SWD), or within 5km of production wells undergoing hydraulic fracturing during the time of the seismic activity. Proximity to the large reservoir impoundment of Greer's Ferry Lake will be noted due to its static weight and periodic loading and unloading. We are developing criteria modified after Davis and Frohlich (1987 and 1993) to rate and assign a probabilistic classification to the clusters of earthquakes as to their likelihood of being natural or induced. This information can be used to help determine whether these earthquakes should be included in future National Seismic Hazard Maps.