横向各向同性介质中弹性波的物理模拟
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摘要
陆相薄互层沉积在一定程度上可以用横向各向同性（TI）介质来描述。通过对一种TI介质的地震物理模拟实验，给出了该介质模型不同观测方式的实验记录，并对介质中的波场、体波速度以及反射波的时差进行了分析，发现TI介质中的波场较各向同性介质中的波场要复杂得多，三种体波在介质中的传播速度随角度的变化也不同。在不同炮检距下，qSH反射波具有相同的瞬时时差速度，而qP和qSV反射波的瞬时时差速度却随炮检距的不同而变化，但在炮检距不大的情况下，可以分别用一个统一的时差速度来近似，但该速度与介质中垂向速度无关。
Landfacies thin bed sediments can be simulated to some extent with transversely isotropic (TI) media. In this paper we give experimental records of a TI medium under different observation pat-tems by means of seismic physical modeling experiments on this medium model. After an analysis of wavefield, body wave velocity and reflection wave moveout in the medium, it is found that the wavefield in TI medium is much more complicated than in isotropic medium and that the propagation velocity variations of these three kinds of body waves with angle are different. When the offset changes, qSH reflected waves have the same instantaneous moveut velocity, but the instantaneous moveout velocities of qP and qSV reflected waves change with the offset. Under the circumstance of small offset, a unified moveout velocity can be used for approximation, which has nothing to do with the vertical velocity in the medium.
Landfacies thin bed sediments can be simulated to some extent with transversely isotropic (TI) media. In this paper we give experimental records of a TI medium under different observation pat-tems by means of seismic physical modeling experiments on this medium model. After an analysis of wavefield, body wave velocity and reflection wave moveout in the medium, it is found that the wavefield in TI medium is much more complicated than in isotropic medium and that the propagation velocity variations of these three kinds of body waves with angle are different. When the offset changes, qSH reflected waves have the same instantaneous moveut velocity, but the instantaneous moveout velocities of qP and qSV reflected waves change with the offset. Under the circumstance of small offset, a unified moveout velocity can be used for approximation, which has nothing to do with the vertical velocity in the medium.
引文
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4 S Crampin and B J Radovich. Imerpetation of synthetic common depth gathers for a single ansotropic layer. Geophysics, 1982,47(3)
5 Leon Thomsen. Weak elastic anisotropy. Geophysics, 1986, 51(10)
6 Xiangyang Li and S Crampin. Approximations to shear-wave velocity and moveout equations in anisotropic media. Geophysical Prospecting, 1993, 41
7 E J Radovich and F K Levin. Instantaneous velocity and reflection times for transversely isotropic solids. Geophysics, 47(3)
8 Patrick N Okoye,Ping Zhao and N F Uren. Inversion technique for recovering the elastic constants of transversely isotropic materials. Geophysics, 1996, 61 (4)
2 G W Postma. Wave propatation in a stratified medium. Geophysics, 1955,20(4)
3 J G Berryman. Long-wave elastic anisotropy in transersely isotropic medium. Geophysics, 1979, 44 (5)
4 S Crampin and B J Radovich. Imerpetation of synthetic common depth gathers for a single ansotropic layer. Geophysics, 1982,47(3)
5 Leon Thomsen. Weak elastic anisotropy. Geophysics, 1986, 51(10)
6 Xiangyang Li and S Crampin. Approximations to shear-wave velocity and moveout equations in anisotropic media. Geophysical Prospecting, 1993, 41
7 E J Radovich and F K Levin. Instantaneous velocity and reflection times for transversely isotropic solids. Geophysics, 47(3)
8 Patrick N Okoye,Ping Zhao and N F Uren. Inversion technique for recovering the elastic constants of transversely isotropic materials. Geophysics, 1996, 61 (4)
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