声波方程数值模拟中的任意广角单程波吸收边界

Arbitrarily wide-angle wave equation absorbing boundary condition in acoustic numerical simulation

地震数值模拟需要使用稳定有效的吸收边界条件,以达到衰减人工截断边界反射的目的。本文将一种高精度单程波方程,即任意广角波动方程(AWWE)用作二阶声波方程的吸收边界条件,采用有限差分法给出边界的计算公式,并对角点进行了特殊处理。均匀模型与解析分析法结果的对比及Marmousi模型波场模拟证实:AWWE用作吸收边界能适用于较大入射角情况,其吸收效果明显优于传统的二阶傍轴近似吸收边界条件(CE2);AWWE吸收边界几乎不增加额外计算量,并且不影响内部区域数值计算的稳定性。

To attenuate artificial edge reflections arising at truncation boundary,stable and effective absorbing boundary conditions(ABC) should be applied in seismic numerical simulation.In this paper,we use a high accurate one-way wave equation,named arbitrarily wide-angle wave equation(AWWE),as ABC in second-order acoustic wave equation simulation.We give out the corresponding discrete formulation of the boundary condition using the finite-difference method.Meanwhile,the corner regions are carefully treated.The numerical simulations of a homogeneous medium and 2D Marmousi model show that AWWE boundary condition can adapt to a wide range of incident angle and has a better absorption effect than second-order paraxial approximations(CE2 in short).The computation efficiency of the AWWE boundary condition is almostidentical to CE2.In addition,such an ABC has noinfluence to the interior stability.