HR: 0800h
AN: U41B-0407    [Abstracts]
TI: Seismic Velocity Structures of a High-Velocity Area Near the Core-Mantle Boundary Beneath Eastern Eurasia
AU: * He, Y
EM: ymhe@mail.igcas.ac.cn
AF: Seismological Laboratory (SKL-LE), Institute of Geology and Geophysics, Chinese Academy of Sciences, No.19 Beituchengxilu, Deshengmenwai, Qijiahuozi, Chaoyang District, Beijing, 100029, China
AU: Wen, L
EM: lwen@notes.cc.sunysb.edu
AF: Department of Geosciences, State University of New York at Stony Brook, Stony Brook, NY 11790, United States
AU: Tang, Q
EM: tqsh@mail.igcas.ac.cn
AF: Seismological Laboratory (SKL-LE), Institute of Geology and Geophysics, Chinese Academy of Sciences, No.19 Beituchengxilu, Deshengmenwai, Qijiahuozi, Chaoyang District, Beijing, 100029, China
AB: The shear and compressional velocity structures of a high-velocity area near the core-mantle boundary (CMB) beneath the eastern Eurasia are studied based on waveform modeling and differential travel time analysis of ScSH-SH and PcP-P phases. Our seismic data are obtained from the F-net in Japan, the Global Seismographic Network and several PASSCAL arrays. The observed ScSH-SH and PcP-P differential travel time residuals show similar patterns, but also a change of P/S velocity ratio across the region. The seismic data suggest that the average shear and compressional velocity increases reach 3% and 2% in the lowermost 300 km of the mantle, respectively. The waveform data from the shear and compressional waves sampling the region can be explained by a model with a D" discontinuity with a large variability of its structure. The data sampling southwest and southeast of the high-velocity area can be explained by simplified one-dimensional models with a D" discontinuity that are characterized by a shear velocity jump of 5% to 3.4% and a compressional velocity jump of 2.6% at about 220 km to 260 km above the CMB followed by a negative gradient toward the CMB. But, the shear wave data sampling the region between would exclude a D" discontinuity with a shear velocity jump greater than 1%. We will discuss effects of two-dimensional wave propagation on the inferred seismic structures and the D" discontinuity, and implication to the origins of the inferred seismic structures in the region.
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 7203 Body waves
DE: 7208 Mantle (1212, 1213, 8124)
SC: Union [U]
MN: 2007 Fall Meeting