A finite difference study on the basement structure beneath the Tianshan Orogen

作     者：ZHAO Junmeng1,2, WANG Qingchen3, GAO Xing1, DUAN Yonghong4, JIA Shixu4 & PAN Shuzhen4 1. Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China 2. Institute of Geology, China Seismological Bureau, Beijing 100029, China 3. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 4. Geophysical Exploration Center, China Seismological Bureau, Zhenzhou 450002, China 

作者机构：Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China Institute of Geology China Seismological Bureau Beijing 100029 China Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China Geophysical Exploration Center China Seismological Bureau Zhenzhou 450002 China 

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

年 卷 期：2004年第47卷第Z2期

页      面：16-23页

学科分类：070904[理学-构造地质学] 0709[理学-地质学] 07[理学] 

基　　金：国家重点基础研究发展计划(973计划) the Altun orogenic belt, the Qiadam basin and the Kunlun orogenic belt (northern margin)(G1999043301) 

主　　题：finite difference, Tianshan orogen, structure of the upper crust. 

摘      要：We use the Pg seismic phase along the Korla-Jimsar profile across the Tianshan orogen and the 3D finite difference method to inverse the velocity structure of the upper crust beneath the basement of this mountain. Based on the velocity structure, the Korla-Jimsar profile can be divided into three parts, i.e. the north edge of the Tarim basin, the Tianshan orogen, and the south margin of the Junggar basin. Within the Tianshan there is a pattern of four convexities and three concavities, which correspond to the southern Tianshan, the Yanqi basin, the middle Tianshan, the Turpan basin, and the Bogda Mountains. In the north edge of the Tarim basin, the basement is about 10km deep with small lateral variations of velocity. In the Tianshan the velocity varies greatly laterally. The basement depth of the Yanqi basin is 6 km, which becomes shallow rapidly northward, and almost to the surface at the middle Tianshan. South to Kumux there is a small intermountain basin, where the maximum basement depth is 3 km, and also turns very shallow near Kumux. The Luntai fault, which bounds the Tarim basin and Tianshan, has vertical dislocation of about 5 km. The Turpan basin is covered with so thick a sediment that its basement is 7 km deep. The boundary fault between the Tianshan and Turpan is the Bolohoro fault which is characterized by quick deepening basement and 7 km vertical dislocation. In the Junggar basin the basement is 8 km deep. On the Korla-Jimsar profile, the velocity distribution of the upper crust and the structure are featured by NS symmetry on both sides of the axis of the Middle Tianshan, consistent with the deep structure revealed by this profile. It means that the Tarim ba-sin and the Junggar basin underthrust toward the Tianshan from south and north, respectively. Such a structural style is different from that of another profile, i.e. the Xayar-Burjing profile, sug-gesting that there may be an important tectonic boundary between these two profiles.