HR: 0800h
AN: T51B-0557    [Abstracts]
TI: Toward Adjoint Tomography of the Japan Subduction Zone
AU: * Chen, M
EM: mchen@gps.caltech.edu
AF: Caltech, 252-21, Caltech 1200 E. California Blvd., Pasadena, Ca 91125, United States
AU: Liu, Q
EM: lqy@gps.caltech.edu
AF: Scripps Institution of Oceanography University of California, San Diego, 9500 Gilman Drive, La Jolla, Ca 92093-0225, United States
AU: Tromp, J
EM: jtromp@gps.caltech.edu
AF: Caltech, 252-21, Caltech 1200 E. California Blvd., Pasadena, Ca 91125, United States
AU: Maggi, A
EM: alessia@sismo.u-strasbg.fr
AF: EOST - IPGS, Université Louis Pasteur, Strasbourg, 67084, France
AU: Kanamori, H
EM: hiroo@gps.caltech.edu
AF: Caltech, 252-21, Caltech 1200 E. California Blvd., Pasadena, Ca 91125, United States
AU: Maeda, T
EM: maeda@bosai.go.jp
AF: NIED, National Research Institute for Earth Science and Disaster Prevention 3-1, Tenno- dai, Tsukuba, Ibaraki, 305-0006, Japan
AU: Obara, K
EM: obara@bosai.go.jp
AF: NIED, National Research Institute for Earth Science and Disaster Prevention 3-1, Tenno- dai, Tsukuba, Ibaraki, 305-0006, Japan
AB: In order to obtain better 3-D seismic velocity models of the Japan subduction zone and the neighboring region beneath Eastern China, we use the adjoint tomography technique to iteratively minimize the misfit between the synthetics and data from Hi-net, F-net and Global Seismographic Network (GSN) stations. We use Zhao et al.\/'s (1994) 3-D model embedded in Lebedev and Nolet's (2003) model as the initial model in the tomographic inversion. According to finite-frequency theory, the sensitive region along the ray path is given by a 3-D `banana-doughnut' kernel, and the overall spatial distribution of the sum of all available event-station kernels determines the resolvable volume in the inversion. We select a total of 300 events with Mw from 4.5--8 to obtain maximum coverage of this region while avoiding redundancy. We processed the data and synthetics using two types of bandpass filters: 6--30~s for all the records and 12--150~s for F-net and GSN records. The adjoint sources are constructed based upon the frequency-dependent traveltime misfit between synthetics and data. Given the adjoint sources, we use the adjoint spectral-element method to calculate banana-doughnut kernels for P, S and surface waves for the selected records. The weighted sums of the banana-doughnut kernels for all event-station pairs, with weights determined by the traveltime measurements, can be used to construct misfit kernels. These gradients will be used in a non-linear conjugate gradient algorithm to further refine the existing 3-D model.
DE: 7200 SEISMOLOGY
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7270 Tomography (6982, 8180)
DE: 8100 TECTONOPHYSICS
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting