VTI介质中准P波方程叠前逆时深度偏移

Prestack reverse-time depth migration of quasi-P wave equations in VTI media

根据具有垂直对称轴的横向各向同性(VTI)介质中的一阶准P波方程,导出了该方程在交错网格中逆时延拓的高阶有限差分格式,给出了其稳定性条件,采用完全匹配层吸收边界条件解决边界反射问题,分别应用下行波最大能量法和归一化互相关成像条件,实现了VTI介质中准P波方程的叠前逆时深度偏移.各向异性Marmousi模型的试算结果表明,VTI介质准P波方程叠前逆时深度偏移算法不受地下构造倾角和介质横向速度变化的限制,对复杂模型具有良好的成像能力;应用归一化互相关成像条件能得到更好的成像效果.对比该模型的各向异性和各向同性逆时偏移剖面表明,在各向异性地区采集的纵波数据用各向异性偏移算法理论上能得到更好的成像结果.

On the basis of first-order quasi-P wave equations in transversely isotropic media with a vertical symmetry axis（VTI）,high-order finite-difference schemes in staggered-grid for reverse-time extrapolation were derived.The stability condition and the perfectly matched layer（PML）absorbing boundary condition for the equations were also provided.Prestack reverse-time depth migration of quasi-P wave equations in VTI media using maximum amplitude method of down-going wave-field and normalized cross-correlation imaging conditions was carried out.Numerical experiments of anisotropic Marmousi model show that prestack reverse-time depth migration of quasi-P wave equations in VTI media has no dip restriction or lateral velocity variation restriction,and has good imaging effect for complex models.Reverse-time migration imaging condition using normalized cross-correlation has better imaging ability.Additionally,the contrast between the imaging results of anisotropic and isotropic reverse-time migration profiles proves that theoretically better imaging results can be obtained using anisotropic migration scheme for P-wave data acquired in anisotropic regions.