Crustal S-velocity structure and radial anisotropy beneath the southern part of central and western North China Craton and the adjacent Qilian Orogenic Belt from ambient noise tomography

作     者：LING Yuan CHEN Ling WEI ZiGen JIANG MingMing WANG Xu 

作者机构：State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China College of Earth Sciences University of Chinese Academy of Sciences Beijing 100049 CAS Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101 China State Key Laboratory of Geodesy and Earth's Dynamics Institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Key Laboratory of the Earth and Planetary Physics Chinese Academy of Sciences Beijing 100029 China 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2017年第60卷第10期

页      面：1752-1768页

核心收录：

学科分类：070801[理学-固体地球物理学] 07[理学] 0708[理学-地球物理学] 

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41225016,91414301&41688103) the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB03010802) 

主　　题：North China Craton Qilian Orogenic Belt Ambient noise tomography Crustal S velocity structure Radial anisotropy 

摘      要：The crustal S-velocity structure and radial anisotropy along a dense linear portable seismic array with 64 broadband seismic stations were investigated from ambient noise tomography with about one-year-long ambient noise recordings. The array transverses the southern part of the central North China Craton(CNCC) and western NCC(WNCC) from east to west and reaches the adjacent Qilian Orogenic Belt(QOB). The phase velocity structures of Rayleigh waves at 5–35 s and Love waves at 5–30 s were measured. The crustal S-velocity structures(Vsv and Vsh) were constructed from the dispersion data(Rayleigh and Love waves,respectively) from point-wise linear inversion with prior information of the Moho depth and average crustal Vp/Vs ratio. The radial anisotropy along the profile was calculated based on the discrepancies between Vsv and Vsh as 2×(***)/(Vsh+Vsv). The results show distinct structural variations in the three major tectonic units. The crustal architecture in the southern CNCC is complicated and featured with wide-distributed low-velocity zones(LVZs), which may be a reflection of crustal modification resulting from Mesozoic-Cenozoic tectonics and magmatic activities. The pronounced positive radial anisotropy in the lower-lowermost crust beneath the Shanxi-Shaanxi Rift and the neighboring areas could be attributed to the underplating of mantle mafic-ultramafic materials during the Mesozoic-Cenozoic tectonic activation. In southern Ordos, the overall weak lateral velocity variations, relative high velocity and large-scale positive radial anisotropy in mid-lower crust probably suggest that the current crustal structure has preserved its Precambrian tectonic characteristics. The low-velocity westward-dipping sedimentary strata in the Ordos Block could be attributed to the Phanerozoic whole-basin tilting and the uneven erosion since late Cretaceous. Integrated with previous studies, the systematic comparison of crustal architecture was made between the southern and nor