HR: 0800h
AN: S51A-0994    [Abstracts]
TI: Development of a Regional Velocity Model Using 3D Broadband Waveform Sensitivity
AU: * Panning, M P
EM: mpanning@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall University of California, Berkeley, CA 94720 United States
AU: Romanowicz, B A
EM: barbara@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall University of California, Berkeley, CA 94720 United States
AU: Kim, A
EM: ahyi@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, 215 McCone Hall University of California, Berkeley, CA 94720 United States
AB: We are developing a new approach which relies on a cascade of increasingly accurate theoretical approximations for computation of the seismic wavefield to develop a model of regional seismic velocity structure for eastern Eurasia using full seismic waveforms. The selected area is particularly suitable for the purpose of this experiment, as it is highly heterogeneous, presenting a challenge for standard modeling techniques, but it is well surrounded by earthquake sources and a significant number of high quality broadband digital stations exist, for which data are readily accessible through IRIS (Incorporated Research Institutions for Seismology) and the FDSN (Federation of Digital Seismic Networks). The initial model is derived from a large database of teleseismic long period waveforms (surface waves and overtone wavepackets) using well-developed theoretical approximations, the Path Average Approximation (PAVA) and Nonlinear Asymptotic Coupling Theory (NACT). These approaches assume waveforms are only sensitive to the 1D (PAVA) and 2D (NACT) structure in the vertical plane between source and receiver, which is adequate for the development of a smooth initial 3D velocity model. We refine this model using a more accurate theoretical approach. We utilize an implementation of a 3D Born approximation, which takes into account the contribution to the waveform from single scattering throughout the model, giving full 3D waveform sensitivity kernels. We perform verification tests of this approach for synthetic models, and show that it can accurately represent the wavefield as predicted by numerical approaches in several situations where approximations such as PAVA and NACT are insufficient. The Born 3D waveform sensitivity kernels are used to perform a higher resolution inversion of regional waveforms for a smaller subregion between longitudes 90 and 150 degrees E, and latitudes 15 and 40 degrees N. To further increase the accuracy of this model, we intend to utilize a very accurate numerical approach, the coupled spectral elements method (Capdeville et al., 2003), for the forward calculations of synthetics. This accounts for nonlinear effects of the structure on the seismograms in addition to the 3D broadband sensitivity.
DE: 3225 Numerical approximations and analysis (4260)
DE: 7255 Surface waves and free oscillations
DE: 7270 Tomography (6982, 8180)
DE: 9320 Asia
SC: Seismology [S]
MN: Fall Meeting 2005