西沙地块海底地震仪转换横波的数据处理与震相识别  

Data processing and seismic phase identification of OBS converted shear wave in the Xisha Block

作　　者：张浩宇 丘学林[1,3,4,5] 王强 黄海波 赵明辉[1,3,4,5] ZHANG HaoYu;QIU XueLin;WANG Qiang;HUANG HaiBo;ZHAO MingHui(Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China;SINOPEC Geophysical Research Institute,Nanjing 211103,China;Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou 510301,China;Southern Marine Science and Engineering Guangdong Laboratory,Guangzhou 511458,China;University of Chinese Academy of Sciences,Beijing 100049,China;Fujian Xiamen Institute of Geological Engineering,Xiamen 361008,China)

机构地区：[1]中国科学院边缘海与大洋地质重点实验室,南海海洋研究所,广州510301 [2]中国石油化工股份有限公司,石油物探技术研究院,南京211103 [3]中国科学院南海生态环境工程创新研究院,广州510301 [4]南方海洋科学与工程广东省实验室,广州511458 [5]中国科学院大学,北京100049 [6]福建省厦门地质工程勘察院,厦门361008

出　　处：《地球物理学报》2021年第11期4090-4104,共15页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41674092,41676045,41730532,42106082,91958212);国家重点研发计划(2018YFC0309800);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0204)联合资助.

摘　　要：主动源海底地震仪(OBS)转换横波震相的分析和模拟,能够从泊松比的角度更准确地约束地下结构和物质组成,有助于地壳精细结构和构造属性的研究.本文对南海北部陆缘西沙地块的OBS2013-3测线进行了转换横波数据处理和分析,通过能量扫描法求取极化角,并对OBS水平分量数据进行旋转,获取了径向分量数据.结合本测线的地质情况,求解佐布里兹(Zoeppritz)方程,得到了不同转换模式的能量分配关系,定量地指示了沉积基底和海底面为主导的P-S转换界面,Moho面为次一级转换界面.在OBS2013-3测线的各个台站径向分量地震剖面上识别出了一系列PPS和PSS型转换震相,最大偏移距达到130km,并进行了初步的正演模拟试算和验证.结合本测线实际情况,对OBS转换横波研究的基础问题进行了探讨.这些工作为后续的二维横波速度结构和泊松比结构模拟、物质组成和地壳属性分析打下了坚实的基础,为研究方法的进一步完善提供思路.Analysis and simulation of converted seismic shear wave phases recorded by active-source Ocean Bottom Seismometer(OBS)provide accurate constrains on subsurface structures and lithological compositions from aspect of Poisson′s ratios,which can facilitate research on detailed crustal structures and tectonic affinity.Processing and analysis of seismic shear wave phases are carried out on OBS2013-3 traversing the Xisha Block,the South China Sea margin.Radial component data is obtained through rotating horizontal components using polarization angles calculated by energy scanning method.Zoeppritz equations are solved based on the geological conditions,which yields the energy partition of different conversion modes,indicating the dominant P-S conversion interfaces of sedimentary basement and seafloor as well as the secondary one of the Moho.A series of PPS and PSS type converted shear wave phases are identified in radial components of most stations of OBS2013-3,whose maximum offset reaches 130 km.Preliminary forward ray-tracing is conducted to verify the identified phases.Based on actual conditions of this profile,we also discuss some fundamental issues in OBS converted shear wave studies.Above work could lay a solid foundation for subsequent 2-D shear wave velocity or Poisson′s ratio modelling and crustal composition analysis,as well as inspire further improvement of research methods.

关 键 词：西沙地块 海底地震仪(OBS) 转换横波 震相识别 转换界面 

分 类 号：P738[天文地球—海洋地质]