HR: 11:05h
AN: S42A-04    [Abstracts]
TI: Mapping The Variations Of Moho Depth And Poisson's Ratio In China With Receiver Function Analyses
AU: * Chen, Y
EM: ychen01@harris.com
AF: Harris Corporation, 1227 S Patrick Dr. Suite 110A, Satellite Beach, FL 32937, United States
AU: Niu, F
EM: niu@rice.edu
AF: Rice University, Department of Earth Science, MS-126 6100 Main Street, Houston, TX 77005, United States
AU: Liu, R
EM: liurf@seis.ac.cn
AF: China Earthquake Network Center, CEA, 5 Minzu Xueyuan S. Road, Beijing, BJ 100081, China
AU: Huang, Z
EM: tw@seis.ac.cn
AF: China Earthquake Network Center, CEA, 5 Minzu Xueyuan S. Road, Beijing, BJ 100081, China
AU: Chan, W
EM: wchan99@harris.com
AF: Harris Corporation, 1227 S Patrick Dr. Suite 110A, Satellite Beach, FL 32937, United States
AU: Sun, L
EM: sunli05@gucas.ac.cn
AF: China Earthquake Network Center, CEA, 5 Minzu Xueyuan S. Road, Beijing, BJ 100081, China
AB: We collected and processed a large amount of high-quality broadband teleseismic waveforms recorded at all 48 stations in the Chinese National Digital Seismic Network (CNDSN) to estimate the lateral variations of Moho depth and crustal Vp/Vs ratio (hence Poisson's ratio) in China by receiver function analyses. A cross-correlation based method was used to select mutually coherent receiver functions, which yielded over 200 traces for most of the stations. Because multiple maxima often present within a thin band in the H-k domain due to the depth- velocity trade-off, we stabilized this method by weighing each H-k grid using the cross-correlation between Ps converted phase and other Moho multiples. An nth-root stacking method was also applied to reduce uncorrelated noise relative to the linear stack. These modifications successfully ruled out any unrealistic results from H-k search. Relatively reliable crustal thickness and Poisson's ratio were consistently obtained from both the RZ (radial and vertical components) and SP (components concentrate SV- and P- wave energy in a skew coordinate system) based receiver function data. Although we utilized average crustal P- wave velocities obtained from Pn/Sn tomographic studies in projecting time to depth, the crustal thickness and Poisson's ratio obtained from receiver functions still show significant discrepancies with those inferred from Pn and Sn waves. For the stations along the east coast of China, the crustal thickness varies from 29km to 37km and the Vp/Vs ratio is about 1.70 on average. While for the stations at the middle section of China across the Sino-Korean platform and the Yangtze platform, the crust turns to be 39km on average, and the Vp/Vs ratios are higher than those to the east coast. The results presented beneath the stations in the west of China well illustrated the complicated and active tectonic complexion in this region. Along the Tianshan fold system, the Moho is at about 53 km on average, whereas in the Tibetan plateau, the Moho could extend to over 80 km. The average Poisson's ratios are a little bit higher than the sub-regions to the east, but are rather lower than that inferred from Pn tomography. The azimuthal variations, as well as complicated crustal and upper mantle structures such as sediment and LVZ beneath some stations have also been observed from receiver functions. These results will assist to constitute initial models in linear and non-linear inversions to obtain a much finer 1-D crustal and upper mantle velocity model beneath each station.
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 9320 Asia
SC: Seismology [S]
MN: 2007 Fall Meeting