Spectral element modeling of seismic wave propagation in visco-elastoplastic media including excess-pore pressure development

Numerical modelling of seismic wave propagation, considering soil nonlinearity, has becomea major topic in seismic hazard studies when strong shaking is involved under particular soilconditions. Indeed, when strong ground motion propagates in saturated soils, pore pressureis another important parameter to take into account when successive phases of contractiveand dilatant soil behaviour are expected. Here, we model 1-D seismic wave propagation inlinear and nonlinear media using the spectral element numerical method. The study usesa three-component (3C) nonlinear rheology and includes pore-pressure excess. The 1-D-3C model is used to study the 1987 Superstition Hills earthquake (ML 6.6), which wasrecorded at the Wildlife Refuge Liquefaction Array, USA. The data of this event presentstrong soil nonlinearity involving pore-pressure effects. The ground motion is numericallymodelled for different assumptions on soil rheology and input motion (1C versus 3C), usingthe recorded borehole signals as input motion. The computed acceleration-time histories showlow-frequency amplification and strong high-frequency damping due to the development ofpore pressure in one of the soil layers. Furthermore, the soil is found to be more nonlinearand more dilatant under triaxial loading compared to the classical 1C analysis, and significantdifferences in surface displacements are observed between the 1C and 3C approaches. Thisstudy contributes to identify and understand the dominant phenomena occurring in superficiallayers, depending on local soil properties and input motions, conditions relevant for sitespecificstudies