利用接收函数、面波频散和ZH振幅比联合反演青藏高原东南缘地壳结构及其动力学意义  

Joint inversion of receiver functions,Rayleigh wave dispersion and ZH ratio for crustal structure in Southeast Tibetan Plateau and its implications for dynamics

作　　者：高天扬 丁志峰[1,2] 王兴臣[1,2] 姜磊 GAO TianYang;DING ZhiFeng;WANG XingChen;JIANG Lei(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Key Laboratory of Seismic Observation and Geophysical Imaging,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局震源物理重点实验室,北京100081

出　　处：《地球物理学报》2021年第6期1885-1906,共22页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41774056,41941016-01,41974100和41604074)资助.

摘　　要：本文利用布设在青藏高原东南缘350个宽频带流动地震台站2011年至2014年记录到的远震体波和面波数据来更好地约束研究区地壳S波速度结构.我们采用分步线性迭代反演算法对远震P波接收函数、瑞雷面波相速度和ZH振幅比进行联合反演获得了研究区高分辨率三维S波速度结构.得到如下结果:(1)在中下地壳主要存在两个低速体,一个从川西北次级块体向西南方向延伸穿过红河断裂进入滇缅泰块体;另一个沿着小江断裂和普渡河断裂分布,向南延伸到24°N左右.且这两个低速体与主要断裂有很好的关联性.(2)两个中地壳通道流是由于滇中次级块体中部(峨眉山大火成岩省内带)的高速异常体对来自青藏高原中部东南方向的中下地壳弱物质流的阻挡而形成,并且我们推测东南侧的地壳流很可能是西北侧的主地壳流沿着安宁河断裂流入.绝大多数地震分布于低速通道流的边界区域,说明低速通道流的存在有助于断裂发生剪切运动而诱发地震.(3)基于以上结果,我们认为除了中下地壳流模型,沿着主要走滑断裂的刚性块体的挤压滑动对于青藏高原东南缘的地壳形变和动力学演化也起着非常重要的作用.(4)在峨眉山大火成岩省内带下方10 km到Moho面总体呈现高速异常,推测可能是二叠纪峨眉山大火成岩省形成时期火山作用和基性超基性岩浆侵入地壳所致.The Southeast Tibetan is located in the transition site between the active plateau and stable Yangtze craton,which has deep and huge faults and severe seismic hazards.Teleseismic body and surface waves in this study were recorded from 2011 to 2014 by 350 temporary seismic stations deployed on the Southeast Tibetan Plateau to better constrain the crustal shear-velocity structure.We jointly invert the Rayleigh wave dispersion(10~60 s period),Rayleigh wave ZH ratio(12~60 s period),and P-wave receiver function(0~12 s)with a stepwise linearized joint inversion method to obtain a high-resolution 3D S-wave velocity structure in the study area.We get the following results:(1)There are two main widespread low-velocity zones(LVZs)in the mid-lower crust.One of the LVZs starts from Chuanxibei Sub-Block and goes across Red River Fault into Yunnan-Myanmar-Thailand Block.The other one follows the trace of Xiaojiang Fault and Puduhe Fault until about 24°N.At the same time,their boundaries correlate well with major fault systems.(2)The two main mid-crustal low-velocity channels are formed by high-velocity anomaly in the center of the Dianzhong Sub-Block(the inner zone of the Emeishan Large Igneous Province(ELIP))hindering the large-scale material flow from the mid-lower crust in the southeast of the central Plateau,and we speculate that the channel to the southeast probably is the main channel to the northwest along the Anninghe Fault.Most large earthquakes in this study region occurred in the boundary zones of the low-velocity channels,indicating that the existence of low-velocity channels contributes to the shear motion of faults and triggers earthquakes.(3)Base on the results,we suggest that in addition to mid-lower ductile flow within these channels,the compression of rigid blocks along the major fault systems also plays a significant role in controlling the crustal deformation and dynamic evolution in southeast Tibetan Plateau.(4)From 10 km below the inner zone of the ELIP to the Moho,the high-velocity anomalies generally a

关 键 词：青藏高原东南缘 联合反演 接收函数 面波频散 ZH振幅比 地壳结构 峨眉山大火成岩省 

分 类 号：P315[天文地球—地震学]