Long runout landslides: The role of frictional heating and hydraulic diffusivity

Natural landslides often exhibit surprisingly large travel distances, and an unexplained decrease in apparent friction coefficient H/L (where H is the drop height and L the travel distance) with increasing slide volume, V. This manuscript investigates a thermo-poro-elastic mechanism operating at the base of landslides that may explain this curious behavior. Simulation results indicate that frictional heating at the shear zone at the base of a landslide, elevates pore fluid pressure and reduces friction, resulting in large sliding velocities and distances. Depth-dependent permeability controls pore pressure diffusion rates from the shear zone, allowing larger slides to maintain high pore pressure for longer times, thus resulting in lower H/L. The numerically obtained relation between V and H/L, agrees with field data of subaerial landslides.