三江造山带中段精细速度结构与各向异性

The collision and extrusion between the Indian and the Eurasian plate have resulted in the rapid uplifting of the Qinghai-Tibet Plateau, strong orogenic movements in the surrounding areas, and lateral escape of large amounts of material. The Sanjiang orogenic belt, in the southeastern of the Tibetan Plateau, not only has complex topography and geologic structures, but also multiple suture belts have turned in this area and converged in the narrow north-south tectonic belt in western Yunnan. And as the necessary region for the escape structure and possible crustal flow, the Sanjiang area is an important "window" for studying the mechanism of growth and deformation on the Tibetan Plateau. This project plans to focus on the studies of high-accuracy velocity structure and seismic anisotropy in the middle part of Sanjiang orogenic belt, based on waveform data from high-density temporary seismic array and National Seismic Network. On the account of ambient noise data and receiver function data, using two inversion methods, the crust-mantle velocity structure with both horizontal and vertical space-distribution are obtained. According to the shear wave splitting technique, the anisotropic distribution image of the whole crust is also obtained. All in all, through the joint interpretation of velocity structure and anisotropy, combined with comprehensive discussion on surface deformation and other geophysical data in this region, this project further discusses the relationship between different fault zones and deep material migration in the region, the deformation of lithosphere mechanism and the deep dynamics process, which can provide new information and evidence for the study of the deep structure and dynamics of the Tibetan Plateau.

印度板块与欧亚板块的碰撞挤压作用导致了青藏高原快速隆升、强烈的造山运动以及大量物质的侧向逃逸。位于青藏高原东南缘的三江造山带不仅具有复杂的地形地貌和地质构造，同时多条缝合带在此区发生转折并汇聚于滇西狭窄的南北向构造带中，是物质逃逸和可能的地壳流的必经区域，因而是研究青藏高原生长和变形机制的重要“窗口”。本项目基于密集流动地震台阵及国家固定地震台网的波形数据，针对三江造山带中段开展高精度速度结构和地震各向异性研究。利用背景噪声和接收函数资料，分别采用两种反演方法，获得一个既有水平分布又有深度分布特征的壳幔速度结构。根据剪切波分裂技术获得全地壳各向异性分布图像。通过速度结构和各向异性的联合解读，并结合区域内地表形变及其他地球物理资料的综合讨论，进一步了解区域内断裂带与深部物质运移的关系，探讨岩石圈壳幔变形机制及深部动力学过程，从而为青藏高原深部结构及动力学研究提供新的资料与证据。

位于青藏高原东南缘的三江造山带不仅具有复杂的地形地貌和地质构造，同时多条缝合带在此区发生转折并汇聚于滇西狭窄的南北向构造带中，是物质逃逸和可能的地壳流的必经区域，是研究青藏高原生长和变形机制的重要“窗口”。本研究收集了青藏高原东南缘地区国家固定地震台网和密集流动地震台阵，利用背景噪声数据获得了三江造山带及其周围地区高分辨率速度结构和方位各向异性分布。同时收集了跨断裂流动地震台阵，利用接收函数得到了研究区全地壳地震各向异性特征。结果显示：1. 三江地区中下地壳低速异常分为两条，一条沿丽江-小金河断裂延伸至红河断裂，另一条在小江断裂带附近。2.各向异性快波方向在川滇菱形块体发生偏转，主要边界为丽江-小金河断裂、红河断裂和鲜水河-小江断裂，这说明这几条断裂的边界作用明显。3. 接收函数各向异性揭示了跨断裂带介质的强烈空间变化，以丽江-小金河断裂带和红河断裂带为界，其西侧各向异性方向平行于主要走滑断层的走向，最大的分裂时间出现在主要的剪切带。综上所述，三江造山带协调着青藏高原东南缘的地壳运动，反映了深部构造作用下块体内部产生的地壳介质变形特征。