基于程函面波成像的华北克拉通岩石圈三维高分辨率S波速度结构研究  

3D High-resolution S-wave velocity structure of the lithosphere beneath North China Craton based on Eikonal surface wave tomography

作　　者：钟世军[1,2] 吴建平[1] 司政亚 朱红彬[2] 王薇 Zhong Shijun;Wu Jianping;Si Zhengya;Zhu Hongbin;Wang Wei(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Beijing Earthquake Agency,Beijing 100080,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]北京市地震局,北京100080

出　　处：《地震学报》2024年第4期578-599,共22页Acta Seismologica Sinica

基　　金：国家自然科学基金(42174117)资助.

摘　　要：利用“中国地震科学台阵探测”项目Ⅱ期和Ⅲ期的流动地震台站以及中国区域地震台网中的部分固定台站的观测资料,采用程函面波成像方法获得了华北克拉通及周边区域10—120 s周期的瑞雷面波相速度分布和高分辨率的三维S波速度结构,并基于该速度模型估算了岩石圈厚度分布。结果显示,华北克拉通内部岩石圈厚度除了存在“西厚东薄”的一级分布特征外,还存在一些更小尺度的差异,包括鄂尔多斯地块内部岩石圈“南厚北薄”、鄂尔多斯地块周缘断陷带岩石圈显著的不均匀减薄以及燕山构造带与其南侧华北平原之间的显著差异等。山西断陷带北部与南部地区上地幔浅部(<100 km)存在不同程度的低速异常,它们被中部的高速异常区所分隔。在150 km以下深度从太行山南缘向北至山西断陷北缘存在一条NNE向展布的显著低速异常带,表明上地幔浅部南北部的低速异常在深部相连。结合已有的其它成像结果,我们推测这些低速异常起源于更深处(>200 km),并与由太平洋俯冲板块的滞留脱水导致的上地幔热物质上涌和小尺度地幔对流等密切相关。燕山构造带与华北平原的岩石圈结构存在明显差异,前者遭受的岩石圈破坏改造程度明显弱于后者,张家口—渤海地震带位于这两种不同壳幔结构的过渡带,地震活动较强,我们认为深部结构和热作用的显著差异,以及青藏高原远场挤压效应的共同作用是导致该区地震活动较强的主要原因。The North China Craton has undergone intensely tectonic reactivation since the Mesozoic,which resulted in lithosphere modification,thinning and destruction,and accompanied by large amount of magmatic activity.The neotectonic movement is strong and destructive earthquakes occur frequently in this region.It is of great significance to obtain medium deformation and structure information in the crust and upper mantle for understanding these process.High-resolution lithosphere structure will provide important basis for understanding a series of scientific issues such as the tectonic deformation of crust-mantle media,the interaction between structural blocks,the deep environment of strong earthquakes,the spatial distribution range and dynamic mechanism of lithosphere thinning and destruction.Many researches about seismic tomography have been carried out in the North China Craton.But,the results of high-resolution of the lithosphere across the whole North China Craton are still few,due to the limitation of observation conditions or range,which limits further analysis on a series of scientific issues.As the rapid development of seismic array observation technology,some high-resolution seismic tomography techniques appear which suitable for dense arrays.The Eikonal surface wave tomography takes into account the bending phenomenon of seismic wave propagation path in complex media,and is suitable for both ambient noise and seismic surface wave.Its lateral resolution is equivalent to the average spacing of stations for arrays with relatively uniform distribution of stations.Considering that the ambient noise tomography is limited to medium and short periods(generally below 40 s),which mainly restricts the depth range from the crust to the top of the upper mantle so that it is difficult to carry out research and discussion on deeper depths.In this study,we choose the surface wave observation data to extract Rayleigh wave phase velocity of medium and long period by Eikonal surface wave tomograph,which can provide constraints o

关 键 词：华北克拉通 程函面波成像 S 波速度 低速异常 岩石圈厚度 显著差异 

分 类 号：P315.63[天文地球—地震学]