联合反演面波和体波研究大别造山带地壳上地幔结构

大别造山带是扬子板块向华北板块俯冲-碰撞的产物，是研究大陆深俯冲—超高压变质带形成—折返等大陆动力学过程的天然实验室。深入研究大别造山带地壳上地幔横波速度结构，是正确理解超高压变质带形成和演化等动力学过程的基础和关键。本项目基于流动台阵观测数据和中国地震台网及区域台网数据，利用背景噪声面波成像结合地震面波层析成像技术，联合反演面波相速度和远震S波走时残差，发挥面波信号与远震S波对横波速度拥有互补的敏感性，采用地震噪声同步和异步互相关、高分辨率线性拉冬变换进行面波模式分离，利用重构的基阶模式面波进行频散测量等最新数据处理技术，研究大别造山带地壳上地幔三维横波速度结构。重点研究壳内高速体、中地壳低速层和上地幔板片状高速体的倾向和深部延伸，以期为大别造山带超高压变质岩的折返动力学机制提供地球物理依据。预期研究成果对认识大陆碰撞造山带形成和演化的动力学机制具有重要科学意义。

The Dabie orogen was formed by the continent-continent collision between the Yangtze Craton and the North China Craton. It is the natural library for continental dynamic study of deep subduction, ultrahigh pressure (UHP) metamorphic belt formation, and exhumation. Research on the crustal and upper mantle shear-wave velocity structure beneath the orogenic belt is the key to better understand the process and evolution of the UHP metamorphic belt. We collect broadband seismic data of the portable seismic array and Chinese National Seismic Network (CNSN) in this region. We construct fine crust and upper mantle shear-wave velocity structure beneath the Dabie orogenic belt, by applying seismic ambient noise, teleseismic surface wave two-plane wave tomography, and joint inversion of surface wave signals and S wave differential traveltimes taking advantages of surface wave signals and S waves sensitive to shear-wave velocities. We will apply two newest techniques during our study: synchronous and asynchronous cross-correlation of ambient noise tomography, and surface wave mode separation by high-resolution Linear Radon Transform (LRT) and dispersion measurements on surface waves only containing the fundamental mode of surface waves. We will focus our research efforts on crustal high shear wave velocities, low shear wave velocity layer in the middle crust, and slab-like high velocity anomaly in the uppermost mantle, which will provide geophysical evidences for the exhumation model of the UHP metamorphic belt. This project will provide important constraints on the understanding of dynamic mechanism of continental orogeny and evolution of orogen in the Dabie orogenic belt.