| 二维初至波层析成像揭示的北祁连—阿拉善南缘浅层地壳结构 |
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| 关键词:North Qilian Orogenic Belt Alxa Block tomographic imaging upper crust velocity structure |
| 基金项目:国家自然科学基金(编号: 41774114; 41590863; 41574093);中国地质调查局项目(编号: DD20190011; DD20179342; DD20160083);国家重点研发计划课题(编号: 2016YFC0600302) |
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| Shallow Crustal Velocity Structure of the North Qilian–Southern Alxa Block Revealed by 2D First-arrival Seismic Tomography |
| The North Qilian orogenic belt–southern Alxa Block is located in the northern region of the Qinghai-Tibet Plateau on its northeastern margin. The crustal structure of the belt records the evolution and coupling relationship, since the Early Paleozoic, between the Qilian Mountains, Hexi Corridor Basins, Heli Mountains, and adjacent basins. Detection of the shallow crustal velocity structure will help to reveal the evolutionary history of the crustal structure and the tectonic deformation in this area. In this study, a shallow upper crust P-wave velocity structure from 2 km underground was obtained by using the first-break (Pg) seismic phase data of a deep reflection seismic profile (225 km long) between the North Qilian orogenic belt to southern Alxa Block, using tomographic inversion. The main characteristics were as follows: the thickness of sedimentary cover in Jiudong Basin is up to 2 km, and the difference in basin depth between north and south may be related to the compression between the Alxa block and Qilian orogenic belt; the average depth of Minle Basin is 1.5 km, and the curves of velocity isolines in the basin reflect different uplifting and denudation rates since the Cenozoic; the sedimentary thickness of Yine Basin is at least 1.5 km, and the occurrence of sedimentary strata in the basin is relatively gentle; Jiudong Basin and the Minle Basin on the north and south sides of Yumushan tectonic belt have virtually the same velocity structure and sedimentary thickness, although the surface elevation difference is nearly 1 km. It can be inferred that the uplift of the Yumushan tectonic belt is related to the backthrust of two faults on the north and south sides. In addition, the P-wave velocity structure obtained by inversion reveals the location of multiple faults and block boundaries that developed along the line, which provides a new evidence for discussing the northward expansion of the northeastern margin of the Qinghai-Tibet Plateau and the compression of the Alxa block. |
| WU Guo-wei,XIONG Xiao-song,GAO Rui,CHEN Xuan-hua,LI Ying-kang,YE Zhuo,WANG Guan,WU Hong-mei.2022.Shallow Crustal Velocity Structure of the North Qilian–Southern Alxa Block Revealed by 2D First-arrival Seismic Tomography[J].Acta Geoscientica Sinica,43(6):843-857. |
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