芦山强震区上地壳速度和泊松比分布特征及其动力学意义  

DISTRIBUTION CHARACTERISTICS AND DYNAMIC SIGNIFICANCE OF UPPER CRUST VELOCITY AND POISSON S RATIO IN LUSHAN STRONG EARTHQUAKE AREA

作　　者：徐志萍[1] 刘巧霞[1] 刘志[1] 田晓峰[1] 王夫运[1] 段永红[1] 林吉焱[1] 邱勇[1] 唐淋[2] XU Zhi-ping;LIU Qiao-xia;LIU Zhi;TIAN Xiao-feng;WANG Fu-yun;DUAN Yong-hong;LIN Ji-yan;QIU Yong;TANG Lin(Geophysics Exploration Center,China Earthquake Administration,Zhengzhou 450002,China;Sichuan Earthquake Agency,Chengdu 610041,China)

机构地区：[1]中国地震局地球物理勘探中心,郑州450002 [2]四川省地震局,成都610041

出　　处：《地震地质》2023年第6期1400-1418,共19页Seismology and Geology

基　　金：国家自然科学基金(42074070);中国地震局地震科技星火计划项目(XH21027)共同资助。

摘　　要：龙门山断裂带南段芦山地区先后发生了2013年芦山M S7.0和2022年芦山M S6.1地震,2次强震的孕育发生与所在区域深、浅地震构造环境、地壳物性结构参数密切相关。研究该区地壳浅部物性结构特征及其与深部动力学过程的映射关系对认识该区的孕震环境具有重要意义。因此,文中利用金川—芦山—乐山深地震测深剖面资料的P波、S波初至波走时数据,采用二维射线追踪走时反演方法获取了沿剖面上地壳的精细P波、S波速度和泊松比值。结果显示:剖面西北段松潘-甘孜块体的上地壳具有高P波、S波速度和低泊松比的特征,而东南段的四川盆地上地壳具有低P波、S波速度和高泊松比的特征。在松潘-甘孜块体和四川盆地之间的龙门山构造带,上地壳P波、S波速度和泊松比等值线形态受区域构造活动控制,与地层产状基本一致,呈近直立趋势展布。龙门山构造带下方沉积基底表现出明显的结构差异,且速度和泊松比等值线形成“V”形特征。龙门山断裂带的上地壳速度、泊松比横向变化梯度大,可能是印度板块和欧亚板块碰撞的远程效应使得青藏高原东缘低泊松比地壳向坚硬的扬子地台(高泊松比)挤压,进而产生地壳垂向变形的直接证据。芦山强震区M S7.0地震的余震主要发生在壳内高、低速和泊松比变化梯级带偏高速和低泊松比的一侧,该区的地震活动既受区域断裂构造的控制,也与上地壳的物性结构特征密切相关。The Longmenshan fault zone is located in the northeastern margin of the Qinghai-Tibet plateau,with an overall direction of NNE and a total length of about 500km.As we have known,the Longmenshan fault zone is the boundary fault between the Bayanqala block and Sichuan basin.Since the Cenozoic,the Longmenshan fault zone has experienced intense tectonic activity and multi-stage magmatic activity,forming a series of active faults with different scales and properties.And Lushan M S7.0 earthquake in 2013 and Lushan M S6.1 earthquake in 2022 occurred in the southern section of Longmenshan fault zone,and the two earthquakes were only 10km far away apart.The generation of the two strong earthquakes is closely related to the seismic tectonic environment and crustal physical structure parameters.So to study the characteristics of shallow crustal physical structure and its relationship with deep dynamic processes,is good for us to understand the seismogenic environment of this area.The wide angle inverse/refraction detection method is an effective means to obtain the physical property parameters of the crust.In this paper we extracted the first arrival travel time data of P-wave and S-wave from Jinchuan-Lushan-Leshan deep seismic sounding(DSS)profile data.The 2D ray-tracing travel-time imaging method proposed by Zelt et al.(1998)was used to obtain the 2D P-wave,S-wave and Poisson s ratio structure of the upper crust in the source area of the Lushan strong earthquake and its adjacent area.Then based on the results of deep crust exploration,seismic distribution characteristics and other geophysical and geological studies in this area,we focus on the response of shallow tectonic environment and deep dynamic processes in the upper crust,and analyze the seismogenic environment and seismogenic mechanism of M6-7 strong earthquakes in this area.The results show that:(1)The crustal velocity and Poisson s ratio are significantly different at different positions of the profile.In the Songpan-Ganzi block,the velocities of P-and S-waves i

关 键 词：芦山强震区 上地壳物性结构 深地震测深剖面 龙门山断裂带中南段 

分 类 号：P315.2[天文地球—地震学]