HR: 17:45h
AN: S42J-05    [PDF]
TI: Sensitivity of Teleseismic Body Waveforms to Near-Source 3D Velocity Heterogeneity
AU: * Kang, D
EM: dkang@memphis.edu
AF: Center for Earthquake Research and Inforamtion, The University of Memphis 3890 Central Ave., Memphis, TN 38152 United States
AU: Langston, C A
EM: clangstn@memphis.edu
AF: Center for Earthquake Research and Inforamtion, The University of Memphis 3890 Central Ave., Memphis, TN 38152 United States
AB: There have been many source studies of teleseismic body waves using the approximation that structure near the source consists of plane layers. Although most authors of these studies will claim excellent results for their source models in terms of synthetic fits to observed waveforms, it is a general rule that there always exist anomalous data that do not seem to be explainable under the assumptions of the modeling study. Although there are many possibilities to explain this anomaly, it seems that near-source 3D velocity heterogeneity is an important factor in forming such teleseismic body waveforms. We address problems in near-source velocity heterogeneity for earthquake data sets to evaluate how such heterogeneity influences the Green's function and resulting source inversions. The teleseismic response of buried moment tensor sources in 3D media can be efficiently computed by using the result of the reciprocal problem of an incident P or S plane wave from beneath the structure. The finite-difference method is used for the plane wave response beneath the source structure and then the reciprocity theorem is applied to simulate the teleseismic body waves for the buried earthquake source(s). Teleseismic data sets from the 1994 Northridge and the 1971 San Fernando earthquakes are modeled to investigate the effect of San Fernando/Los Angeles basin structure on teleseismic waveforms. The frequency dependence of the near-source effect is investigated theoretically for proposed structure models and is constrained by detailed geological and geophysical studies in the literature.
DE: 7200 SEISMOLOGY
DE: 7203 Body wave propagation
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting