Effects of multilayered porous sediment on earthquake-induced hydrodynamic response in reservoir

Sediment in a reservoir can be inhomogeneous and layered due to the natural sedimentation process, which highly complexes the hydrodynamic response in the reservoir. Based on an extended transmission and reflection matrix (TRM) method developed in this study, an analytical solution to hydrodynamic response of a water-multilayered porous sediment-bedrock system due to SV wave incident from the bedrock is presented. The uniqueness of the method is that it not only can well accommodate porous sediment with multiple layers, but also is convenient to implement compared to global matrix method. Thus the method is able to reasonably reflect the effects of sediment heterogeneity. The analytical solution is effectively verified against the solution proposed by Wang et al. [28]. Comprehensive parametric study is conducted to investigate the effects of sediment heterogeneity and wave characteristics on the hydrodynamic response in reservoir. Resonant frequencies exist and change with incident angle. Sediment heterogeneity highly influences the hydrodynamic response of the system, especially when the sediment is unsaturated. For sediment with relatively low degree of saturation, the sediment heterogeneity in terms of consolidation level significantly affects the hydrodynamic response at higher order resonant frequencies. Sediment can be divided into numerous layers to reflect the sediment heterogeneity with depth. With the increase of frequency, the needed layer number to precisely describe the sediment heterogeneity increases.