Comparative analysis on spatiotemporal pore pressure evolution under surface-wave perturbations

The near surface spatiotemporal pore pressure fluctuations in a porous half space induced by seismic surface-wave perturbations in different poroelastic regimes are analytically compared. The results for the pore pressure in the space-time domain are derived by inverse transforms of the fundamental solutions of dynamic poroelasticity in the frequency-wavenumber domain. Different poroelastic regimes depend on the different low frequency approximation for Biot's multi wave mode physical behaviors. In low seismic frequency band, whereas the fast wave mode inference can generate surface wave along the interface, fluid pressure is also significantly perturbated as in solid phase, but behaves as a slow P2 mode reflected by the R surface wave. It is also shown that the amount of induced pore pressure fluctuations are different by P2 diffusivity (dispersion-difusivity regime, DD and non-dispersion-diffusivity regime, NDD) and P2 wave (full-wave regime, FW). The strong solid and fluid coupling on the interface generates the transferred RP2 mode. Therefore, the decoupled viscoleastic approximation (VA) does not represent these near surface fluid characteristics. The results can be applied to predict near surface pore pressure responses under seismic perturbations, or as a benchmark for other numerical approaches for pressure solutions in a dynamic poroelastic half space, and also favor a potential interpretation for near surface soil liquefaction failure.