With the continuous research in seismology, the influence of the heterogeneity caused by microstructure interactions of the medium on seismic wave propagation has been paid more attention. Wang et al. (2020) proposed to describe the complex microstructures of the medium in the framework of the generalized continuum mechanics theory, and derived the asymmetric elastic wave equations containing the characteristic length scale parameter of the medium. In addition, scale effects of seismic wave propagation will appear when considering microstructures of the medium. In this work, in order to better analyze the scale effects and extract the new components of wave fields owing to the microstructure interactions, we propose an optimized finite-difference (FD) method based on the improved bat swarm optimization (BSO) algorithm. Then the optimized FD method is used to perform numerical modeling for the asymmetric elastic wave equations considering microstructures of the medium. Numerical dispersion analysis indicate that the optimized FD method has high accuracy. According to the numerical modeling results obtained by the optimized FD method, scale effects of seismic wave propagation can be clearly observed when considering microstructures of the medium.

随着地震学研究的不断深入，介质微观结构相互作用引起的非均质性对地震波传播的影响受到越来越多的关注。王等人。(2020)提出在广义连续介质力学理论框架下描述介质的复杂微观结构，并推导了包含介质特征长度尺度参数的非对称弹性波方程。此外，考虑介质的微观结构时，还会出现地震波传播的尺度效应。在这项工作中，为了更好地分析尺度效应并提取由于微观结构相互作用而产生的波场的新分量，我们提出了一种基于改进的蝙蝠群优化（BSO）算法的优化有限差分（FD）方法。然后采用优化的FD方法对考虑介质微观结构的非对称弹性波方程进行数值模拟。数值色散分析表明优化后的FD方法具有较高的精度。根据优化FD方法获得的数值模拟结果，考虑介质的微观结构时，可以清楚地观察到地震波传播的尺度效应。