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在弹性波有限差分正演模拟中,吸收边界条件常用来吸收截断边界处引入的不期望边界反射,其中完全匹配层(PML)吸收边界条件被认为是目前最理想的吸收边界条件。但是PML吸收边界条件的传统实现却存在着很大不足:全局分裂式PML吸收边界条件实现简单但是需要占用太多内存;局部分裂式PML吸收边界条件需要考虑多个边界和角点区域,编程实现非常复杂;非分裂式PML吸收边界条件由于涉及卷积运算,计算量很大。本文基于非分裂式PML吸收边界条件,结合复频移伸展函数,提出了一种新的数值实现方法,其计算方程简单、占用内存小、编程实现容易,是对PML介质理论数值实现的改进和完善。
In the finite difference forward modeling of elastic wave, the absorption boundary conditions are often used to absorb the undesired boundary reflections introduced at the truncated boundary, where the perfect matching layer (PML) absorption boundary conditions are considered as the most ideal absorption boundary conditions. However, the traditional implementation of PML absorption boundary conditions has a great shortage: the global split PML absorption boundary conditions to achieve simple but need to take up too much memory; partial split PML absorption boundary conditions need to consider multiple boundary and corner regions, the programming Very complex; Non-split PML absorption boundary conditions are computationally intensive due to the convolution calculations involved. Based on the non-splitting PML absorption boundary conditions, combined with the complex frequency shift expansion function, a new numerical method is proposed, which has the advantages of simple calculation equation, small occupation memory and easy programming. It is an improvement on the numerical realization of PML medium theory and perfect.