利用宽角地震数据研究青藏高原西缘板块汇聚带地壳结构

The cenozioc subduction and collision from India continent to the Eurasia plate has brought significant impacts on the regional topography and environments, such as crust shortage of thousands kilometers and horizontal extrusion of Tibetan plateau crust. However the contact relationship among different blocks and the crustal deformation are not clear so far.The orogenic history of Tibetan plateau has been concentrated at western Tibetan plateau where the deep process and surface response of the convergence between this two plates have been recorded, and the huge Karakorum strike-slip fault developed. Thus western Tibetan plateau afford us a ideal window to know the continental-continental collision and its effects.Here we propose to construct a north-south multi-attributes crust structure profile which is along the longitude 80 E, 380km long and locate at the east side of the Western Himalayan Syntax: we firstly invert the crust P-wave and S-wave velocity structure, the poisson ratio, the attenuation factor, and the Moho geometry from the wide-angle reflection/refraction seismic data respectively, and then the results are going to be intergrated to discover the fine structure of the crust. We'll try to find the deep background related to shallow and surface tectonics, and the crust reflection features related to continental collision process. This can afford us a few signifcant constraints and evidences upon the research of the continental subduction and colision together with its correlation with the huge Karakoram strike-slip fault belt, therefore it can play a most active role in promote our understanding about the contact relationship and crust ddeformation accompany with the evolution of Tibetan plateau.

新生代以来印度板块对欧亚板块的俯冲碰撞和持续作用引起上千公里的地壳缩短并伴随青藏高原地壳物质横向挤出，然而青藏高原不同块体接触关系及其内部变形方式仍然是当前地学界关注的焦点。青藏高原西缘浓缩了青藏高原的演化史，记录印度板块与欧亚板块汇聚的深部过程及地表其响应，并具有规模巨大的喀喇昆仑走滑断裂，为深入理解陆陆碰撞造山及其效应提供了理想的实验场地。本项目拟基于该地区东经80 附近的宽角反射/折射地震资料，反演地壳纵横波速度、泊松比、衰减属性及莫霍界面形态等，构建青藏高原西构造结东侧南北向380km长的多属性地壳结构剖面，揭示研究区浅表构造发育的深部背景以及与陆陆碰撞造山过程相关的壳内反射结构特征，并为探讨其与喀喇昆仑断裂之间的关联提供来自地壳深部的约束和证据，深化对青藏高原演化过程中块体接触关系和地壳变形方式的认识。

青藏高原西缘记录了新生代以来印度板块与欧亚板块的汇聚历史，为深入理解青藏高原陆陆碰撞造山及其壳内形变响应提供了理想实验场地。自然科学面上基金项目“利用宽角地震数据研究青藏高原西缘板块汇聚带地壳结构”获得多种研究成果：基于该地区札达-泉水沟剖面252台数字地震仪采集的人工源宽角地震资料，通过相关反演成像方法反演获得上地壳纵横波速度，通过偏移成像揭示全地壳反射结构，利用Rayinvr技术反演全地壳纵波速度结构及莫霍界面形态、以及利用同剖面22台宽频带地震仪采集的全球天然源地震资料对壳内结构进行接收函数成像并反演了全地壳横波速度结构。以上多种特征综合构建了青藏高原西构造结东侧南北向380km长的多属性地壳结构剖面，揭示出研究区浅表构造发育的深部背景以及与陆陆碰撞造山过程相关的壳内反射结构特征，为深入理解青藏高原西缘构造演化过程、块体接触关系和地壳变形方式等提供了来自地壳深部的科学证据。