Upper Mantle Anisotropy Beneath North China

详细信息   

• 责任者：Chang Lijun (Institute of Geophysics ; China Earthquake Administration ; Beijing 100081 ; China) ; Wang Chunyong
• 刊名：Chinese Journal of Geophysics
• 出版年：2012
• 卷期：55(3)
• 关键词：上地幔 ; upper mantle ; 各向异性 ; anisotropy ; 华北地区 ; North China
• 页码：p.886-896
• 图表：5 illus., 46 tables, 1 ref.
• 分类号：0400
• issnNo：ISSN0001-5733
• isbnNo：CN11-2074/P

摘要

Based on the polarization analysis of teleseismic SKS（SKKS） waveform data recorded at 200 broadband and very-broadband stations in the North China Seismic Array,the fast-wave polarization direction and the delay time between the fast and slow shear waves at each station were determined by using the grid searching method of minimum transverse energy and the stacking analysis method,and the published results of permanent stations also were cited,and then we acquired the image of upper mantle anisotropy in North China.The fast-wave directions are basically NWW-SEE in Eastern North China,while the fast-wave directions rotate to NW-SE and NNW-SSE in Western North China.The delay time falls into the interval [0.50 s,1.47 s].The average delay time of Western North China is less than that of Eastern North China.In Eastern North China,the fast polarization direction is consistent with the absolute plate motion（APM） direction,implying that the NWW-trending asthenospheric mantle flow driven by the APM plays a major role in observed upper mantle anisotropy beneath Eastern North China,and makes the alignment of upper mantle peridotite lattice parallel to the deformation direction,and thus generates consistently the NWW-trending fast polarization direction.However,in the stable Western Block,the weak anisotropy observed is possibly attributed to the ＂fossil＂ anisotropy frozen in the thick lithosphere of ancient cratonic NCC.