Resolution Earthquake Location in the New
Madrid Seismic Zone
Dunn, Steve Horton, Heather
DeShon, and Christine Powell
relocations are being calculated in
the New Madrid Seismic Zone (NMSZ) using the Double Difference
algorithm developed by
Waldhauser and Ellsworth (2000). The New
Madrid Seismic Zone is one of the few places on Earth where earthquakes
frequently without the presence of a plate boundary.
Double-Difference relocations are especially
useful in areas where the distance between neighboring events is small. Our dataset consists of 1394
recorded between 2000 and 2006. The
catalog data consists of approximately 280,000 P-wave observations and
S-wave observations from 197 stations.
The inversion of catalog data alone produces small changes in
original earthquake locations. Tests show that a high P to S velocity
(>3) in the shallow surface layer has little effect on locations
inverting synthetic data. Waveform cross-correlation travel time
have been computed. The cross-correlation data and the catalog data are
incorporated into the inversion using a variety of weighting schemes. Results using both cross-correlation and
catalog data exhibit a tightening of hypocenters within individual
the seismic zone. The robustness of these
results is being established through the use of additional synthetics.
Double-Difference tomography algorithm developed by Zhang (2003) will
also be used
with the catalog and cross-correlation data from this study to produce
three-dimensional P- and S-wave velocity model of the region.