基于P波接收函数资料的华南大陆东部地壳结构研究  

Crustal structure in eastern areas of South China block based on P-wave receiver functions

作　　者：聂仕潭 段永红[2] 谭萍 檀玉娟[2] 赵延娜[2] NIE ShiTan;DUAN YongHong;TAN Ping;TAN YuJuan;ZHAO YanNa(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,China;Institute of Disaster Prevention,Sanhe Hebei 065201,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe Hebei 065201,China)

机构地区：[1]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [2]中国地震局地球物理勘探中心,郑州450002 [3]防灾科技学院,河北三河065201 [4]河北省地震动力学重点实验室,河北三河065201

出　　处：《地球物理学报》2023年第10期4149-4161,共13页Chinese Journal of Geophysics

基　　金：国家自然科学基金青年基金项目(42204063,41174052);河北省自然科学基金项目(D2020512005)资助。

摘　　要：华南大陆是由扬子块体和华夏块体拼合而成,并经历了多期次的后期改造,研究块体间的深部结构差异对于理解华南大陆的构造演化历史具有重要意义.本文基于布设在华南大陆东部的流动宽频带地震台阵资料,计算了远震事件的P波径向接收函数,并利用Pms谐波分析方法获得了地壳各向异性分布.结果显示,研究区地壳各向异性具有明显的横向分段特征.JSF(江绍断裂带)附近与断裂带走向一致的地壳各向异性快波方向指示断裂带可能切穿整个地壳.在大别造山带、扬子块体和华夏块体南部,地壳各向异性快波方向与区域主压应力方向近垂直,指示该区域地壳变形可能受菲律宾海板块俯冲和太平洋板片俯冲后撤的远程效应的影响.此外,本文利用新的H-κ-c叠加方法获得了测线下方地壳厚度及平均波速比.结果显示,扬子块体的地壳厚度薄于两侧的华夏块体和大别造山带,速度比也较低(约1.7),指示地壳以长英质和酸性岩石为主.Airy地壳均衡理论预测的地壳厚度指示29°N以南的地壳密度要低于以北的区域.以南的低密度及低波速比可能与菲律宾海板块北西向俯冲和太平洋板块西向俯冲后撤导致的地壳物质垂向分异拆沉有关.The South China block is composed of the Yangtze block and Cathaysia block and has undergone several stages of late transformation.It is of great significance to study the deep structural differences among the blocks for understanding the tectonic evolution history of the South China block.Based on the data of the broadband seismic array located in the eastern South China block,we calculated the P-wave radial receiver functions,and obtained the crustal anisotropy based on the Pms harmonic analysis.The results show that the crustal anisotropy of the seismic array has obvious regional characteristics.The fast wave directions near JSF(JiangShao fault)are consistent with the strike of the fault,indicating that the JSF may cut through the entire crust.In the Qinling-Dabie orogenic belt,the Yangtze block and the southern Cathaysia block,the fast wave directions are nearly perpendicular to the regional principal compressive stress direction,reflecting that the crustal deformation in this region may be influenced by the remote effect of subduction of the Philippine Sea plate and the Pacific plate.We also measured the crustal thickness and the average VP/VS ratio using H-κ-c stacking method.The crustal thickness of the Yangtze block is thinner than that of the Cathaysia block and the Qinling-Dabie orogenic belt with lower VP/VS ratios of approximately 1.7,which indicates that the crust is dominated by felsic and acidic rocks.The crustal thickness obtained by Airy isostasy theory shows that the crustal density is lower in the south of 29°N than that in the northern regions.The low density and low VP/VS ratio in the south of 29°N may be related to the vertical differentiation and delamination of crustal material caused by the northwestward subduction of the Philippine Sea plate and the westward subduction and retreat of the Pacific plate.

关 键 词：华南大陆 接收函数 地壳各向异性 地壳厚度 波速比 

分 类 号：P315[天文地球—地震学] P313[天文地球—固体地球物理学]