考虑水层鸣震的海底多分量数据转换波走时反演方法  

Travel-time inversion for converted waves of ocean-bottom multi-component seismograms considering water-layer reverberations

作　　者：刘学义 程玖兵[1] 王腾飞[1] LIU XueYi;CHENG JiuBing;WANG TengFei(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China)

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092

出　　处：《地球物理学报》2021年第9期3316-3332,共17页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2018YFC0310104);国家自然科学基金(42074157,41630964)资助.

摘　　要：海底多分量地震数据在完成上-下行P/S波分离之后,基本消除了检波器端的多次波信号,但仍受到一些源端多次波的干扰.在浅水(水深在500 m以内)、软海底环境下,经海底与海面各反射一次的水层鸣震因能量较强,对反射波偏移成像与速度分析造成极大的困扰.就横波速度分析而言,含源端水层鸣震的PPS波对一次转换PS波形成主导性干扰.本文从走时反演的视角,基于声波方程建立描述PS波和PPS波的Born模拟算子,提出同时拟合这两种S波震相的反射走时反演方法及相应的梯度预条件技术.合成数据实验表明,该方法可克服源端强水层鸣震的影响,改善转换波走时拟合条件,提高横波速度反演精度.After up-down and P/S decomposition of ocean-bottom multi-component seismograms,pure up-going waves are still interfered by source-side multiples even though receiver-side free-surface related multiples are eliminated.In the setting of soft seafloor and shallow water(less than 500 m water depth),strong water-layer reverberations reflected by the seabed and sea-surface can bring great trouble to seismic imaging and velocity analysis of reflection data.In analysis of shear wave velocity,the primary converted PS waves are dominantly contaminated by source-side reverberations,namely PPS waves.This work attempts to solve these problems.From the perspective of travel-time inversion,we derive Born modeling operators for PS and PPS waves based on the acoustic wave equation,and then propose a reflection travel-time inversion method that simultaneously fits these two S-wave phases with appropriate gradient preconditioning.Tests on synthesis data show that this method can tackle strong source-side water-layer reverberations,improve the travel-time fitting for converted waves and enhance the accuracy of shear wave velocity model.

关 键 词：转换波 水层鸣震 波动方程走时反演 海底地震仪 P/S分离 

分 类 号：P631[天文地球—地质矿产勘探]