基于高密度地震台阵/台网三重震相的青藏高原东南缘岩石圈-软流圈三维速度结构研究

During the closure of Tethys ocean, many microplates combined, and then the India plate collided with the Eurasia plate, nowadays the Tibet plateau has become the youngest and highest plateau in the world. The clockwise tectonic rotation, tectonic faults, destructive earthquakes, multiepisode magma activities have happened in south-eastern Tibet. Probing 3D seismic wave structure of lithosphere-asthenosphere beneath this area, especially the existing of low velocity layers in the lithosphere can make insight into the geodynamic process of subduction of Tethys ocean, rifiting of the Tibet plateau, movement process of deep material and Cenozoic volcano activities. Using seismic triplications recorded by the high density portable seismic array in Yunnan and China National Seismic Network in the Yunnan-Sichuan region, the P and S wave 3D velocity structures can be obtained by the comparison between synthetic and observed seismic triplications, and then the topography of LAB, low velocity layer, and low or high velocity anomalies, and Poisson's ratio can obtained from the seismic structures. Combined with the results from tectonics and geochemistry, our study can provide the fundamental parameters for analyzing the tectonic evolution of the south-eastern Tibet plateau.

经过各期特提斯洋的闭合、各微板块拼贴及后期印度板块与欧亚大陆的陆陆碰撞，青藏高原成为了世界上最年轻、最高大的高原。青藏高原东南缘显现出顺时旋转模式，加之其间发育有众多大断裂带、破坏性大的强震及多期次的岩浆活动，探测该区域岩石圈－软流圈三维地震波速度结构，特别是岩石圈内的低速层的存在，对认识各期特提斯洋板块俯冲、深部物质运移过程和新生代以来的岩浆活动等相关的地球动力学过程具有重要意义。本项目拟利用云南高密度流动台阵及中国数字地震台网川滇地区台站所积累的地震观测资料，基于P和SH三重震相合成地震图和观测波形走时及波形拟合对比，给出P波、S波三维速度结构，进而获得岩石圈－软流圈边界的起伏形态、泊松比、高速/低速异常体的存在，结合构造地质、地球化学等结果。综合分析岩石圈内部及底部低速层、局部速度异常体与地幔俯冲残留体分布及岩浆活动的关系，为认识青藏高原东南缘的构造演化过程提供基础参数。

经过各期特提斯洋的闭合、各微板块拼贴及后期印度板块与欧亚大陆的陆陆碰撞，青藏高原成为了世界上最年轻、最高大的高原。青藏高原东南缘显现出顺时旋转模式，加之其间发育有众多大断裂带、破坏性大的强震及多期次的岩浆活动，探测该区域岩石圈－软流圈三维地震波速度结构，特别是岩石圈内的低速层的存在，对认识各期特提斯洋板块俯冲、深部物质运移过程和新生代以来的岩浆活动等相关的地球动力学过程具有重要意义。本项目拟利用云南高密度流动台阵及中国数字地震台网川滇地区台站所积累的地震观测资料，基于P和SH三重震相合成地震图和观测波形走时及波形拟合对比，给出P波、S波三维速度结构，进而获得岩石圈－软流圈边界的起伏形态、泊松比、高速/低速异常体的存在，结合构造地质、地球化学等结果。综合分析岩石圈内部及底部低速层、局部速度异常体与地幔俯冲残留体分布及岩浆活动的关系，为认识青藏高原东南缘的构造演化过程提供基础参数。