各向异性弹性波叠后逆时深度偏移

Poststack reverse-time depth migration for anisotropic elastic waves

中国科学院地质与地球物理研究所, 北京 100101

Geological and Geophysical Research Institute of Chinese Academy of Sciences, Beijing 100101, China

大量数据表明地下岩层的地震各向异性是普遍存在的。然而在常规偏移中,通常视地下介质为各向同性介质,这必然导致一定的误差。研究了各向异性弹性波的有限元逆时延拓算法及有关人工吸收边界条件等问题,实现了各向异性弹性波有限元逆时深度偏移系统。2个理论模型的自激自收资料实算表明,该系统能够清晰准确地进行偏移成像。另外,对这两个模型资料的各向同性偏移证实,常规各向同性偏移剖面上存在较大误差。

A large amount of data shows that seismic anisotropy widely exists in underground terranes. But in traditional migration, people usually consider subsurface as isotropic media. So some errors may be resulted. The paper studied issues of reverse-time continuation algorithm and absorbing boundary conditions of anisotropic elastic waves, and materialized a poststack reverse-time depth migration system with finite element method. The migrated results of two models show that the system can produce clear and accurate images of complex geological structures, whereas the isotropically migrated results for the same models suggest that traditional isotropic migration can cause considerable errors.