An Investigation of the Microseismicity at the Newberry EGS Site

Abstract

We aim to increase the amount of information that can be extracted from continuous seismic data collected in an Enhanced Geothermal System (EGS). To accomplish our objective, we apply a seismic imaging technique that can map seismicity from known discrete microearthquake sources using the Matched Field Processing (MFP) method. We investigate the seismic activity within the DOE Newberry EGS site and identify more and smaller microearthquakes than with the traditional STA/LTA method. For example, between October – December 2012 the official catalog identified 204 events while the MFP technique identified 249 additional events. For the events with the highest signal-to-noise ratio, we apply a local Bayesian multiple-event seismic location algorithm that estimated the 95% ellipsoids of the posterior mean locations. The results show that the upper and lower seismic swarms are most probably activating two separate areas of the reservoir. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.