2D各向异性TTI介质中地震波场的射线法和波动方程数值模拟对比

Seismic wavefield propagation on 2D anisotropic TTI media through ray theory and wave-equation simulation and comparison

尽管射线理论是基于波动方程高频假设下的一种近似理论,两者本应相互佐证共同发展完善,然而实际上确是平行独立的.鉴于此,本文提出了一种可以相互验证波场数值模拟或射线追踪数值模拟方法正确性和有效性的佐证方法.为了实现上述目的,我们首先将用于各向同性介质中多次波预测的分区多步不规则最短路径算法推广至各向异性TTI介质中,使其具备追踪各向异性TTI介质中多次波的能力.然后,通过伪谱法波场数值模拟和分区多步不规则最短路径算法预测得到的波场快照图、单炮地震记录剖面、以及合成理论地震图的分析对比,不但可以相互验证两种算法的正确性和有效性,同时对地震波在各向异性TTI介质中的传播规律和特点有了深刻的理解和认识.结果表明:本文提出的各向异性介质中多次波射线追踪算法是正确有效的.

Despite of ray theory based on high frequency assumption of wave-equation, the ray theory and the wave-equation simulation methods should be mutual proof for each other and jointly developed, but in fact parallelly independent. For this purpose, we in this paper put forward a mutual verification method to test the accuracy and efficiency of both ray theory and wave-equation method in anisotropic TTI medium. To fulfill this goal, we first extended a multistage irregular shortest-path method, previously developed for isotropic medium for multiple arrival tracking, to the anisotropic TTI medium to trace multiple arrivals. Through the analysis and comparison of wavefield snapshot, common source gather seismic profile and synthetic seismogram by using the pseudo-spectral method for wavefield modeling and the multistage irregular shortest-path method for multiple arrival tracking, it is not only able to verify the accuracy and efficiency of each method, but also capable of thoroughly understanding the wave propagation laws. The results show that the multistage irregular shortest-path method in anisotropic TTI for multiple arrival tracking in this paper is correct and efficient.