HR: 17:45h
AN: S32E-08    [PDF]
TI: A Lithospheric Study of Eastern Asia Using Surface Wave Dispersion
AU: * Pasyanos, M E
EM: pasyanos1@llnl.gov
AF: Lawrence Livermore National Laboratory, L-205 P.O. Box 808, Livermore, CA 94551 United States
AU: Walter, W R
EM: walter5@llnl.gov
AF: Lawrence Livermore National Laboratory, L-205 P.O. Box 808, Livermore, CA 94551 United States
AU: Flanagan, M P
EM: flanagan5@llnl.ogv
AF: Lawrence Livermore National Laboratory, L-205 P.O. Box 808, Livermore, CA 94551 United States
AB: We have continued our study of surface-wave group-velocity dispersion across Eastern Asia in the vicinity of the Korean Peninsula, Yellow Sea, and Sea of Japan. We primarily use seismic data from permanent stations in South Korea, China, Japan, Taiwan and Russia. We also use data from several IRIS PASSCAL deployments in China and North Korea. We measure group-velocity using multiple narrow-band filters on deconvolved displacement data. We use a conjugate gradient method to perform a high-resolution group-velocity tomography over the region. Our current results include Rayleigh wave inversions for periods from 10 to 100 seconds. There is an excellent correspondence between the group velocities and tectonic structure, including large sedimentary features and crustal thickness variations. At long periods ($>$ 50 sec), we find that the inversion has features associated with the subduction of the Pacific and Philippine Plates under the Eurasian continent, including the effects of the subducting slab and magmatic arc. We use the group-velocity results to model the shear-velocity structure of the crust and upper mantle across the region. We employ a grid-search technique to fit the Rayleigh wave group-velocities over the whole period range. This does a very good job at retrieving features in the crust and uppermost mantle. Deeper features in the mantle, however, are harder to model directly using this method. To resolve these features, we will be forwarding modeling the structure by constructing several models of the subduction zone. We will then be testing the various models by comparing the group velocities predicted by the models to the observed group velocities along cross-sections. Preliminary results indicate that the magmatic arc has the largest affect on the long period surface waves, with the subducting slab being a much subtler feature.
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 7220 Oceanic crust
DE: 7255 Surface waves and free oscillations
SC: Seismology [S]
MN: 2003 Fall Meeting