| Title | An Investigation of the Microseismic Events in the Salton Sea Geothermal Field |
|---|---|
| Authors | Jingbo WANG, Dennise C. TEMPLETON, Dave B. HARRIS |
| Year | 2012 |
| Conference | Stanford Geothermal Workshop |
| Keywords | microseismicity, signal processing, event detection, geothermal, Salton Sea, Coulomb stress |
| Abstract | We present a new method for microearthquake event detection. We have adapted the Matched Field Processing (MFP) technique, originally developed to locate continuous underwater acoustic sources, to detect transient microearthquake signals. We create templates derived from existing catalog events and compare these master templates to the continuous seismic data stream with the aim to identify more events than the current available catalog events. We call this method the empirical MFP method. We propose that empirical MFP can complement existing earthquake catalogs and techniques by significantly increasing the number of earthquakes that can be detected on existing seismic networks. For example, in the Southern California Earthquake Data Center (SCEDC) earthquake catalog, 333 events are listed as occurring in the Salton Sea Geothermal Field (SSGF) during January 2011. By examining all events in the SSGF between 2008 and 2010 we identified 231 master template events. We compare these master templates to the continuous seismic data and successfully identify 1526 events as occurring in the SSGF during January 2011. This is over a 450% increase in the number of events detected. We investigate the optimal frequency bands and threshold levels for which the empirical MFP method works best in our study area. Since faults interact with elastic stress changes, we utilize focal mechanism information from the micro-earthquakes to study the static stress redistribution in the SSGF. We calculate the Coulomb stress change using faults elements provided by a focal mechanism catalog during a three-month period from November 2009 to January 2010 when two major earthquake swarms occurred. We then compare the stress field with the hypocenters of the seismic swarm events to investigate the effectiveness of Coulomb stress modeling to predict the locations of smaller swarm events using larger swarm events in the SSGF. |