| 基于解耦传播的波场分解方法在VTI介质弹性波逆时偏移中的应用 |
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| 引用本文： | 周进举,王德利,李博文,李强,王睿.基于解耦传播的波场分解方法在VTI介质弹性波逆时偏移中的应用[J].吉林大学学报(地球科学版),2018(3):909-921. |
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| 作者姓名： | 周进举 王德利 李博文 李强 王睿 |
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| 作者单位： | 吉林大学地球探测科学与技术学院,长春,130026 |
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| 基金项目： | 国家自然科学基金项目(41374108)，国家科技重大专项子课题(2016ZX05026-002-003)Supported by National Natural Science Foundation of China(41374108)，Major Projects of the National Science and Technology of China(2016ZX05026-002-003) |
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| 摘 要： | 由于弹性波逆时偏移更符合实际情况,而且转换波的成像结果有更高的分辨率,因此弹性波逆时偏移越来越受到重视。然而,弹性波逆时偏移需要多波多分量数据,为了减少成像结果中的串扰假象,在逆时偏移过程中进行P波和S波分解就变得非常必要。结合基于向量的激发振幅成像条件,我们把基于解耦传播的波场分解方法应用到弹性波逆时偏移中,并对比了其在各向同性介质和横向各向同性(VTI)介质中的应用效果。结果说明,该方法可以在各向同性介质中完全分解P波和S波,并保留波场的向量信息。虽然在VTI介质中有较小的分解残余,但是该分解残余不会在逆时偏移结果中产生明显的串扰;因此,这种波场分解方法可以应用于各向同性介质和VTI介质弹性波逆时偏移。该方法是在时间空间域实现的,可以在波场传播过程中直接对P波和S波进行分离,应用方便,计算效率高。与利用Helmholtz分解的弹性波逆时偏移相比,该方法避免了在PS波成像结果中的极性反转问题。在复杂Hess VTI模型的逆时偏移结果中,高速岩体和断层的成像清晰,甚至是两个低速薄夹层也能较好成像;这说明该方法对复杂介质具有较好的适应性。PS波成像结果中的各向异性体成像清晰,说明各向异性介质弹性波逆时偏移可以对传统逆时偏移不能很好成像的构造进行成像。
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| 关 键 词： | 叠前弹性波逆时偏移 波场分解 解耦传播 VTI介质 prestack elastic reverse time migration wavefield decomposition decoupled propagation vertically transversely isotropic (VTI) media |
Application of Wavefield Decomposition Based on Decoupled Propagation in Elastic RTM for VTI Media |
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| Zhou Jinju,Wang Deli,Li Bowen,Li Qiang,Wang Rui.Application of Wavefield Decomposition Based on Decoupled Propagation in Elastic RTM for VTI Media[J].Journal of Jilin Unviersity:Earth Science Edition,2018(3):909-921. |
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| Authors: | Zhou Jinju Wang Deli Li Bowen Li Qiang Wang Rui |
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| Abstract: | Since the elastic reverse time migration (RTM) is more representative to the actual situation,and the converted-wave RTM results have high resolution,the study of elastic RTM draws more and more attention in the recent years.Because multicomponent data is required by the elastic RTM method,and its wavefield contains both P-and S-waves,before imaging we need to separate the P-waves from S-waves so as to avoid the crosstalk.Combining with the vector-based excitation amplitude imaging condition,we applied the wavefield decomposition method based on the decoupled propagation to the elastic RTM and analyzed its application in the isotropic and vertically transversely isotropic (VTI) media.The results demonstrated that the method perfectly decomposed P-and S-waves in the isotropic media and preserved the vector information also.Although there were some small residuals in the separated wavefield for the VTI media,this residual did not generate obvious artifacts in the RTM results.Therefore,this wavefield decomposition method can be applied in the elastic RTM for an isotropic and VTI media.This method is realized in time-space domain.The separation of P-and S-waves can be directly separated during the wavefield propagation conveniently and efficiently.Compared with the elastic RTM using Helmholtz decomposition,this method avoids the problem of polarity reversal in the PS images.The migration results of the complex Hess VTI model showed that the high-velocity rock mass and a fault were clearly imaged,and even two low-velocity thin interlayers were well imaged.This suggests that the method is better adaptive to a complex model.The PS images can present a relative clear image of an anisotropic body.It demonstrates that the anisotropic elastic RTM can be used to image some subsurface structures better than the conventional RTM. |
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