跨多期次台阵资料探测天山-塔里木盆山系统岩石圈精细结构

The crustal shortening and thickening mechanism and its seismo-tectonic environment of the Tienshan-Tarim basin and range system is of great importance on the dynamic evolution of the Tienshan orogen. High resolution crust and lithosphere structures are key issues on deciphering these problems. However, due to the unevenly distributed observations, especially the asynchronous deployed seismic arrays, the spatial resolution of the crustal and uppermost mantle seismic image is too low to constrain the crustal deformation mechanism and the seismogenic environment for the Tienshan-Tarim basin and range system. In this project we propose to collect data from permanent network and the asynchronous campaign arrays, as well as collect the data from the campaign array in the Tarim basin which is deploying by the member of this project. Then we apply the C3 method which is developed in the recent years to process the data, so that to combine data from multiple asynchronous arrays. During the data process, we first calculate ambient noise correlation functions between the campaign stations and the permanent stations, then we calculate the correlation functions between the coda of the correlation functions (C3) between the asynchronous stations and the permanent stations. Based on the C3 functions we combine the asynchronous arrays together, so that improve the path coverage for the studied region significantly. After obtained C3 functions between all of the seismic stations, we propose to make a joint inversion with C3 functions, ambient noise empirical Green's functions, surface wave data and receiver functions to obtain high resolution isotropic and anisotropic crustal and lithospheric shear wave structures. Moreover, in order to further combine the asynchronous seismic array data, so that further improve the spatial resolution of crustal velocity structures, we propose to make a joint inversion with C3 functions, surface wave and local earthquake body wave data, and build high precision and high resolution Vp, Vs structures, as well as precise earthquake distributions. Finally we analyze possible crustal shortening mechanism and seismogenic environment of the Tienshan-Tarim basin and range system by combining seismic velocity structures, earthquake properties and geodynamic models.

天山-塔里木盆山系统的地壳增厚缩短机制和发震构造对于认识天山动力学演化研究具有重要意义，而高分辨率的地壳上地幔速度结构是认识该机制的关键。然而该区域的观测分布不均匀且非同期，导致天山-塔里木系统的地壳和岩石圈结构分辨率很低，严重影响了对动力学和发震构造的认识。本项目通过新发展的C3方法，收集固定台网和不同期台阵数据以及本项目成员布设在塔里木盆地的台阵数据，计算流动台阵与固定台站的噪声格林函数，并对尾波进行相关性计算，获得不同期台站间的C3格林函数，从而整合不同期数据。然后将C3格林函数与面波以及远震接收函数进行联合反演，得到塔里木和盆山系统的岩石圈剪切波精细结构。为了进一步整合不同期台阵数据，本项目将C3格林函数、面波与近震体波进行联合反演，得到高分辨率Vp、Vs及地震位置。结合波速结构与地震性质及动力学信息，探讨天山-塔里木盆山系统的地壳缩短机制和发震构造。

天山-塔里木盆山系统的地壳增厚缩短机制对于天山动力学具有重要意义，高分辨率的地壳上地幔顶部速度结构和发震构造是认识该动力学机制的关键。然而该区域的观测没有在同时期进行，导致对天山-塔里木盆山系统的地壳上地幔结构的了解比较差，严重影响了对动力学、发震构造和震源性质的认识。项目的研究内容为：通过新发展的C3方法，收集固定台网和不同期流动台阵数据，计算流动台阵与固定台站的噪声格林函数，并对这些台站与固定台站噪声格林函数的尾波进行相关性计算，获得不同期台站间的C3格林函数，从而将不同期台阵的数据整合起来；反演该区域的地壳上地幔速度结构。在此基础上，结合地震数据，发展震源性质反演方法，确定该区域的动力学机制及发震构造特征。在项目资助下，我们首先进一步发展了C3方法，针对C3方法中噪声格林函数的尾波互相关函数信噪比很低的问题，我们分别测试和对比了不同的叠加方法；以及发展了利用噪声格林函数的直达波进行互相关的方法，分别对比分析C3的直达波互相关以及尾波互相关函数的特征，提高了C3互相关函数的信噪比。发现直达波互相关函数能够大大提高不同期背景噪声互相关函数的信噪比，从而大大增加可用的台站对数量。同时，我们发展了台站矫正方法、面波传播偏离大圆路径导致的方位角偏差矫正方法、各向异性反演方法、接收函数harmonic stripping分解及接收函数与面波联合反演方法等，为反演地下速度结构及各向异性提供了基础。再次基础上，我们反演了该区域及中国大陆其他地区的岩石圈结构及各向异性，研究了地震的震源参数及发震构造，并分析了中国大陆主要区域的地震危险性。在本项目的支持下发表了14篇SCI论文、1篇核心期刊论文，并培养了11名研究生。项目发展的方法为研究地壳和岩石圈结构、发震构造提供了技术支撑，成像的结果和震源性质的研究为认识天山造山带及中国其他区域的发震构造和地震危险性提供了依据。