Detecting Events Beyond the Catalog - Applying Empirical Matched Field Processing to Salton Sea Geothermal Field Seismicity

We apply the empirical Matched Field Processing (MFP) method to continuous seismic data obtained from the Salton Sea Geothermal Field to detect and locate more micorearthquakes than can be detected using only traditional earthquake detections methods. The empirical MFP method compares the amplitude and phase of the incoming seismic data to a set of pre-computed master templates. The master templates are created from previously observed earthquakes with good signal-to-noise ratio. We will relocate the seismicity using two different methods: hypoDD and BayesLoc. hypoDD is a double-difference earthquake relocation method that utilizes absolute P- and S-wave travel-time measurements and cross-correlation P- and S- wave differential travel-time measurements to determine high-resolution relative hypocenter locations (Waldhouser and Ellsworth, 2000). BayesLoc is a probabilistic (Bayesian) multiple-event locator that simultaneously provides a probabilistic characterization of the unknown origin parameters, corrections to the assumed travel-time model, improvements in the precision of the observed arrival-time data and accuracy of the assigned phase labels (Myers et al., 2007, 2009). Additionally, we will model the Coulomb stress changes, assuming the seismicity is due to an opening or shearing crack. We will match the location of the modeled stress increases with the locations of the mapped seismicity using a grid-search method.