Viscous boundary, viscous spring boundary, infinite boundary have been widely used during the last decades to solve the wave propagation in the infinite ground. In this paper we evaluate the performance of the three boundary conditions focusing on their solution precision. The comparison is performed on a two dimensional finite element model built by ABAQUS. The results show that viscous spring boundary outperforms the other boundary conditions, and viscous boundary is better than infinite element.

The MASW method is robust in determine shear wave velocity of shallow site because the dispersive properties of Rayleigh wave was dominated by shear wave velocity of subsurface. Using this method, an assumption that the earth model is one dimensional and horizontal layered must be put to simplify the real earth model without considering the lateral variation. However, it is not always the truth. In order to obtain a two dimensional S-wave velocity profile of shallow site, a CMP cross-correlation (CMPCC) method was proposed by Hayashi and Suzuki (2004) to approximate two dimensional S-wave velocity profile with one dimensional inversion procedure. In order to verify its approximate resolution, a horizontal stepped layer model and a dipping layer model were chosen. The synthetic wave fields of the two models were calculated by staggered grid finite difference method. Result shows that this method can only be used to approximate horizontally stepped layer model and cannot be used to approximate dipping layer model.