作　　者： (张伟）; (石颖）;

机构地区： 东北石油大学地球科学学院,大庆163318

出　　处： 《地球物理学进展》 2017年第4期1728-1734,共7页

摘　　要： 弹性波逆时偏移是当前多分量地震资料相对准确的偏移算法,它能够形成多波模式的成像剖面,从而减少纵波勘探的多解性.本文首先依据各向同性介质中矢量分离纵横波场的速度-应力方程组,利用高阶交错网格有限差分数值方法求解弹性波方程,进而构建矢量的纵波和横波波场,不同于散度和旋度算子分离纵横波场的传统方法,文中提出的矢量分离纵横波场方法保持了原始波场的振幅和相位特征.文中也提出将震源归一化的内积成像条件应用于分离后的纯纵波和横波矢量场,由此得到的转换波成像避免了传统弹性波成像方法中出现的极性反转.水平层状和复杂构造模型测试表明,文中提出的基于矢量分离纵横波场的弹性波逆时偏移方法成像精度高,转换波成像PS和SP极性无反转,所形成的多种模式纯波剖面能够准确地对复杂地下构造成像. Elastic reverse time migration based on two-way elastic wave equation is a relatively accurate migration algorithm in processing multi-component seismic data,it can produce accurate subsurface information（e.g.PP and PS reflectivity）.In this paper,we first exploit high-order staggered grid finite difference method to solve elastic wave velocity-stress equation of P-and Swaves decomposition.Unlike the traditional decomposition method that apply curl and divergence operators,vector decomposition of Pand S-waves can＇t lead to distort amplitude and phase of the input wavefields.Therefore,we do not need additional correction calculation for wavefields decomposition.Then,we propose to apply the source normalized inner product imaging condition between those separated vector wavefields,which avoids crosstalk between unseparated wave modes and gains more explicit physical meaning images between pure mode waves.Moreover,PS and SP images automatically avoid polarity reversal which inherently occurs in traditional imaging method with scalar and vector potentials.Tests with synthetic example show that elastic reverse time migration based on the vector decomposition gains PS and SP images without polarity reversal.And,it produces images which can accurately characterize subsurface structure.

关 键 词： 弹性波逆时偏移 多分量地震资料 矢量分离 内积成像条件 极性反转