Influence of viscous coupling on seismic reflection and transmission in saturated porous media

Wave propagation in saturated porous media involves complicated couplings between the solid skeleton and pore fluid. In particular, viscous coupling plays a key role because in general it makes wave propagation dispersive and dissipative. Although the importance of the viscous coupling in wave propagation in an unbounded saturated medium was recognized, the knowledge of its effect on the reflection and transmission from a saturated porous boundary is limited. A detailed investigation is therefore carried out in this article on the influence of viscous coupling in the reflection and transmission at an interface between saturated porous media and ordinary elastic media. The interface is considered to be either permeable or impermeable to include the effect of hydraulic boundary condition. In particular, the dependence of viscous coupling effect on the hydraulic condition at the interface is studied in this article. The variations of the reflection and transmission coefficients with the angle of incidence as well as the frequency for different values of viscous coupling are computed and compared for permeable interface and impermeable interface. In addition, the seismic reflection in two extreme cases of viscous coupling, that is, null viscous coupling and infinite viscous coupling, is discussed. The results indicate that the effect of viscous coupling is complicated; it depends strongly on the hydraulic condition at the interface as well as the frequency of the incident wave. Additionally, it depends upon the angle of incidence.