On effective characteristic of Rayleigh surface wave propagation in porous fluid-saturated media at low frequencies

The analytical dispersion and waveform solutions of Rayleigh surface wave for the Biot fluid-saturated model are obtained at low frequencies for a homogeneous half space. The equivalent solution is also obtained by the equivalent-viscoelastic representation of the fluid-saturated model based on a single viscoelastic element for each wave modulus. The effective characteristics of the validations and limitations for the equivalent-viscoelastic model are analyzed by comparison of the numerical solutions of the fluid-saturated model and the equivalent model for the surface wave propagations. Our calculations show that the free boundary effects on the frequency dependent dispersion and time dependent dynamical waveforms of the surface wave in the Biot model are well fitted in a relative narrow low frequency band by the Zener elements in case of the frequency is much lower than the critical frequency f c of the porous material. The effective characteristics for air filled cases with a higher f c show a better result. Furthermore, if the critical frequency f c is low, always with high permeability κ under near surface condition, at low frequencies (e.g. the seismic frequency band