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地震波沿自由表面传播P波和S波干涉会产生面波现象。因此,地震波数值模拟中需要精确地处理自由表面边界以获取面波传播的数值解。本文提出了一种基于动态孔弹性理论包含自由表面边界处理的时空域交错网格有限差分数值计算方法。针对自由表面,推广弹性介质中的传统应力镜像自由边界处理方法,提出一种新的描述孔隙介质固体和流体自由边界特征适用于面波模拟的应力镜像法。自由表面所在网格节点上的相应镜像的处理就能获得稳定精确的面波数值解。数值模拟得到的第一类Rayleigh波的结果表明该算法在相应的弹性介质中一样的网格剖分下就可获得保证精度的稳定解。数值模拟的例子反映了本文所述方法的有效性。
Seismic wave propagation along the free surface of P wave and S wave interference will produce surface wave phenomenon. Therefore, the numerical solution of seismic wave numerical simulation needs accurate treatment of free surface boundary to obtain surface wave propagation. In this paper, a finite-difference numerical method for calculating the staggered-grid space-time domain based on dynamic hole elasticity theory is proposed. Aiming at the free surface, the traditional stress mirror free boundary treatment in elastic media is extended. A new stress mirror method is presented to describe the characteristics of free boundary of solid and fluid in porous media. The processing of the corresponding image on the mesh node where the free surface is located can obtain a stable and accurate surface wave numerical solution. The results of numerical simulation of the first Rayleigh wave show that the proposed algorithm can obtain a stable solution with guaranteed accuracy under the same meshing in the corresponding elastic medium. The numerical simulation example reflects the validity of the method described here.