各向同性弹性波逆时偏移
Isotropic elastic reverse time migration
陈生昌 1李代光 1龚新月1
作者信息
- 1. 浙江大学地球科学学院,杭州 310027
- 折叠
摘要
为了得到物理意义明确、地质可解释的偏移成像结果,当前的弹性波逆时偏移方法需要在偏移过程中对外推的弹性波场进行P/S波分解,以消除物理上相互不匹配的波型在偏移成像结果中产生的交叉噪声.给定具有地震波运动学特征准确的地下介质光滑模型,本文首先给出了作为地震数据线性反演的偏移所对应的一般正演表达式;再利用各向同性弹性波方程,推导出了适合弹性介质光滑模型的P/S波解耦的弹性波方程,即纵波弹性波方程和横波弹性波方程;最后对各向同性弹性波逆时偏移提出了新方法和新认识.对于纯P(或S)波震源激发得到的地震数据的各向同性弹性波逆时偏移,提出了对外推的弹性波场无需进行P/S波分解,在偏移成像结果中也不会出现交叉噪声的新方法;对于P/S波复合震源激发得到的地震数据的各向同性弹性波逆时偏移,提出了即使对外推的弹性波场进行P/S波分解,在偏移成像结果中还会出现交叉噪声的新认识.
Abstract
In order to obtain the migration imaging results with clear physical meaning and geological interpretation,the current elastic reverse time migration methods require P/S waves decomposition to the extrapolated elastic wavefields in the migration process to eliminate the cross-talk artifacts generated by physically mismatched wave modes in the migration imaging results.Given a smooth model of subsurface media with accurate kinematic characteristics of seismic waves,this paper first proposes a general forward representation for migration as a linear inverse problem of seismic data.Then,by using the isotropic elastic wave equation,the P/S wave decoupled elastic wave equations suitable for the smooth model of elastic media are derived,namely a P wave elastic wave equation and a S wave elastic wave equation.Finally,a new method and new realization for the isotropic elastic reverse time migration are proposed.For the reverse time migration of isotropic elastic wave seismic data excited by the pure P(or S)wave source,a new method is proposed,which does not need the P/S waves decomposition to the extrapolated elastic wavefields and does not appear cross-talk artifacts in the migration imaging results.For the reverse time migration of isotropic elastic wave seismic data excited by P/S waves composite source,a new realization is put forward that even if the P/S waves decomposition is used to the extrapolated elastic wavefields,the cross-talk artifacts still appear in the migration imaging results.
关键词
弹性波/光滑偏移模型/逆时偏移/无P/S波分解/交叉噪声Key words
Elastic wave/Smooth migration model/Reverse time migration/Without P/S waves decomposition/Cross-talk artifacts引用本文复制引用
基金项目
国家自然科学基金(42274145)
国家自然科学基金(U19B2008)
出版年
2024
NETL
NSTL
万方数据