A New Method for Event Detection and Location
— Matched Field
Processing Application to the Salton Sea Geothermal
Field
We present a new method for microearthquake event detection
and location. 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
previously identified earthquake signals and compare these master templates to
the continuous seismic
data
stream to detect previously unidentified 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.
We also apply Coulomb stress modeling to understand
earthquake interaction and fault orientation in the SSGF. We calculate Coulomb
stress change using focal mechanism information and compare it with the
locations of seismic events to investigate the effectiveness of Coulomb stress
modeling to reflect possible fault opening or shearing.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California