SLIP BELOW AN ELASTIC THIN LAYER TYPE LANDSLIDE MODEL

Abstract

This research focuses on the dynamics of slow slip (or creep) reactivation in landmasses triggered by fluid injection, which induces landmass movement. We examine a basic mechanical model of the continental sheet in which differential slip occurs at the base of a thin, deformable slab. Elastic deformation of the thin layer is seen, and the friction at the base is thought to be state-dependent and slip-rate dependent. By diffusively spreading across the base at a consistent injection rate, the fluid lowers the effective normal stress. We investigate how pore-pressure radiation along the base may cause the interface's frictional strength to decrease, which in turn may encourage slip at the base. In order to replicate the dynamics of the basal slip, the model takes into account three physical processes: (i) elastic deformation of the thin slab, (ii) slip rate, and history-dependent (iii) pore-pressure diffusion along the base of the thin slab. We find that the pore-pressure source can alone re-activate slip without any external driving stress. The pre-stress along the fault and pore pressure both dictate the development of slip. The interplay of these three physical processes results in a system of three partial differential equations that describe the evolution of slip rate, slip state, and pore pressure along the base of the layer. We numerically solve the coupled partial differential equations method of lines. To calculate the derivatives, we use MATLAB’s FFT subroutine. We find that pore pressure diffusion can lead to rapid slip when basal frictional properties are rate-weakening (a/b > 1). The pore-pressure diffusion can lead to slow aseismic creep when basal frictional properties are rate-strengthening (a/b < 1). For rate-strengthening case, we use self-similar solution for pore pressure diffusion and numerical solution for slip rate and state evolution. In the latter part of this study, we also examine the impact of topographic variations on the surface profile of the elastic thin layer model. By incorporating the surface profile as an arbitrary sinusoidal trigonometric function, we integrate it into our system of coupled differential equations and analyse its effect on the slip rate.