Kirchhoff向下延拓法在海洋合成多道地震走时反演中的应用  

Application of Kirchhoff downward-continued method to travel-time inversion of synthetic multi-channel seismic data

作　　者：张茂传 徐敏[1,3] 赵旭 张佳政[1,3] 查财财 Vithana MVP[1,2] 狄会哲 曾信 ZHANG Maochuan;XU Min;ZHAO Xu;ZHANG Jiazheng;ZHA Caicai;Vithana MVP;DI Huizhe;ZENG Xin(Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou 510301,China;University of Chinese Academy of Sciences,Beijing 100049,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511548,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,南海生态环境工程创新研究院,广东广州510301 [2]中国科学院大学,北京100049 [3]南方海洋科学与工程广东省实验室(广州),广东广州511458

出　　处：《热带海洋学报》2020年第4期80-90,共11页Journal of Tropical Oceanography

基　　金：国家自然科学基金项目(41676044、91858207、41890813);中国科学院战略性先导科技专项(XDA13010105);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(GML2019ZD0205)。

摘　　要：海洋多道地震数据建模和成像是获取洋壳速度和构造信息的重要手段。海水层的存在使得多道地震拖缆接收到的折射波走时信息仅仅存在于较远的炮检距,近炮检距被强振幅海底反射波覆盖,制约了走时数据拾取和反演效果。本文基于波动方程的Kirchhoff积分法,成功实现了多道地震数据向下延拓,获取到了更大炮检距区间的初至折射波走时拾取,并将其应用于洋中脊新生洋壳2A/2B层的合成多道地震数据走时反演。比较向下延拓前后的走时拾取范围及走时反演结果表明,向下延拓法能够保持地震波场的运动学和动力学特征不变,在共炮集数据的更大炮检距范围内进行初至折射走时拾取,从而增加反演的数据选择和浅层射线覆盖,反演结果能更加准确地分辨出洋壳2A/2B层界面,并得到更高的分辨率和更准确的速度结构剖面。Velocity model building and seismic imaging from marine multi-channel seismic(MCS) data are essential to obtain the structural information of oceanic crust. Existence of the seawater layer makes first-arrival refraction phases recorded by streamer only existed in far offset, while most of them in near offset are masked by the strong amplitude seafloor reflection phase, affecting travel-time picking and inversion. Based on the Kirchhoff integral approach to wave equation, we successfully implement the downward continuation(DC) method to the MCS data, and obtain first-arrival travel-time picks within a wider offset range. The method is applied to the synthetic MCS data simulated based on layer 2 A/2 B structure of newborn crust along a mid-ocean ridge, and first-arrival picking range and inversion result are compared before and after the DC. The DC method can expand offset range for first-arrival refraction picking and increase the ray coverage in the shallow depth, without changing the kinematics and dynamic characteristics of seismic wave field. The inversion results can more precisely distinguish the layer 2 A/2 B interface, and obtain higher resolution and more accurate velocity profile.

关 键 词：海洋多道地震 Kirchhoff积分 向下延拓 走时反演 洋壳2A/2B层 

分 类 号：P738.4[天文地球—海洋地质]