面波和体波联合成像研究华南南部陆内造山带的岩石圈深部结构

In South China, the widespread mineralization during the Mesozoic and the Cenozoic is related to the multi-episode extensional deformation of the lithosphere. At the same time, its lithosphere has experienced and recorded continent–continent collision and intracontinental orogenic processes in various stages. Detection for lateral variations of lithospheric structures can provide constraints and evidences for the study of the deformation mechanisms in the multi-phase intracontinental orogenic domain of South China and the structural property of Xuefengshan orogen, and the southwestern boundary of Yangtze and Cathaysia blocks. Surface and body wave tomography are major approaches to obtain lithospheric structures. Surface wave tomography generally has a good depth resolution. Its detection depth increases with the wavelength, but the resolution decreases as depth increases. For the body wave, it go through mantle and can detect deeper structures than surface wave, but its constraint for the shallow structure is poor. In this study, we plan to apply a joint inversion using surface wave dispersion and finit frequency body wave traveltimes to image the lithospheric structures for southern part of South China, using a combination dataset of regional permanent stations and portable seismic stations deployed by Guilin University of Technology. In the objective function of the joint inversion, a relative weight factor is used to balance the different sensitivities of surface and body wave data, which can compromise advantages of surface wave and body wave imaging methods, and then obtain a reliable velocity structure of the lithosphere. Based on the obtained lithospheric structures within the research area, we will explore the southwestern boundary of Yangtze and Cathaysia blocks, structural property of Xuefengshan orogen and the intracontinental orogen domain. The results will provide more information to explain the deep process of the multi-phase intracontinental orogen and the related tectonic deformation.

发生在华南地区的中、新生代大规模成矿作用与岩石圈多阶段伸展变形有关。同时，该地区岩石圈经历了不同时代的陆陆碰撞及陆内造山，记录了多期次板块聚散过程。探测岩石圈深部介质横向结构特征可为研究华南复合陆内造山区变形机制及雪峰山造山带的构造属性、厘定扬子与华夏块体的西南段边界位置等提供约束和证据。地震面波和体波层析成像是获取岩石圈速度结构的重要手段。面波探测深度随波长增加，但分辨率随之降低；远震体波探测深度深，但对浅部结构约束弱。为获取华南南部的壳幔深部结构，本研究拟利用区域固定台站和桂林理工大学布设的流动台站宽频带地震波数据，开展面波频散和有限频体波走时联合层析成像研究。在联合反演目标函数中利用相对权重因子来平衡面波和体波数据不同的敏感性，实现面波和体波成像系统优势互补，获得可靠的岩石圈速度结构，从而深入探讨华南陆内造山区及雪峰山造山带的构造属性、变形机制及相应的深部动力学过程。

利用面波对垂向变化敏感以及远震体波对介质横向变化敏感的互补优势，本研究开展面波和体波数据联合层析成像方法研究，并且体波成像部分采用有限频层析成像方法，可以获得相比使用单一数据更可靠的结果且具有更高分辨率。基于华南地区的人工源地震探测的地壳速度模型、面波层析成像的壳幔速度结构构建初始速度模型，通过层析成像反演方法获取华南南部区域的三维壳幔速度结构。通过将地壳和上地幔的剪切波速度结构横向变化特征与不同构造区域间的构造特征进行对比分析，了解造山带壳内、岩石圈变形特征，在此基础上探讨了扬子板块和华夏板块碰撞拼合西南边界、雪峰山造山带的构造属性、陆内造山的深部成因等。