HR: 0800h
AN: S11B-1024    [Abstracts]
TI: Synthetic Earthquake Location Tests in Southern California
AU: * Lin, G
EM: gulin@ucsd.edu
AF: University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0225 United States
AU: Shearer, P
EM: pshearer@ucsd.edu
AF: University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0225 United States
AB: Our goal in this study is to improve earthquake locations in southern California by understanding the biasing effects of 3-D velocity structure on the observed travel times. We generate synthetic data sets using the actual station and earthquake locations and the pick distribution for data between 1984 and 2002. We begin by considering two test regions: Region A, which encloses much of the San Jacinto and Elsinore Faults and includes 48,050 events with 544,413 P-picks and 156,681 S-picks recorded by 185 stations; and Region B, centered on the Big Bear region, which includes 31,502 events with 517,981 P-picks and 106,957 S-picks recorded by 192 stations. Following single-event location based on optimal 1-D velocity models, we examine the residual patterns to gain insight regarding the scale of velocity variations and station terms. We present maps of source-specific residuals for different stations and plots of residual correlation and MAD (Median Absolute Deviation) differences between event pairs binned by their separation distance. We estimate random picking error for P and S picks from the intercept of the MAD plot as the event separation distance goes to zero. Next, we create synthetic data sets with the same source-receiver geometries as the real data and approximately the same statistical properties by computing travel time anomalies for random 3-D velocity structures. Our results provide insight regarding how to adjust parameters in the source-specific station term (SSST) method to match residual statistics and obtain optimal results. We will present location results for these regions, obtained use both using phase pick and waveform cross-correlation data.
DE: 7260 Theory and modeling
DE: 7299 General or miscellaneous
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting