Discrete element analysis of earthquake surface fault rupture through layered media

Abstract

The influence of soil inhomogeneity on earthquake surface fault rupture is analyzed using the discrete element method (DEM). Particle assemblages are produced with layers having contrasting relative density. Similar to that observed in homogenous soil simulations, loose layers tend to absorb the localized shear deformation from underlying dense layers and disperse it over a broader area. However, the rupture can re-localize as it moves into an overlying dense layer. The ground surface deformations produced by fault rupture through layered soils are bounded by the ground surface deformation produced in homogeneous soil. The presence of a thin layer does not significantly alter the path of fault rupture propagation of a steeply dipping dip-slip fault. Conversely, a loose thin layer within dense soil can divert the path of fault rupture propagation during shallow reverse fault rupture by providing a kinematically compatible path of low shear resistance. Stresses are homogenized within the simulations to highlight the capability of DEM to capture the response of granular materials in scenarios that are difficult to achieve physically in the laboratory.