Seismo Lab Seminar

Fluids are thought to play an important role in both seismic and aseismic fault slip. Permeability controls how fast fluid flows and thus how fast earthquakes migrate. Motivated by experimental evidence, I introduce a permeability evolution law. Permeability increases with slip and decreases with time. Using this evolution law in earthquake sequence simulations, we show the emergence of swarm-like seismicity triggered by constant pressure injection. The parabolic migration front of the seismicity agrees well with the analytical solution for aseismic slip, even though there is negligible aseismic slip. Next, using a linear stability analysis, I discover a novel frictional instability that occurs even for velocity-strengthening friction. This fault valve instability manifests itself as an aseismic slip pulse in numerical simulations. I also simulate megathrust earthquakes and slow slip events in the subduction zone. The simulation results reproduce the depth-dependent recurrence interval of slow slip. Finally, I use a petrological model of metamorphic fluid production in the Cascadia subduction zone to calculate fluid pressure and frictional and viscous strength profiles. I find that the effective normal stress decreases rapidly below the frictional-viscous transition depth. This is consistent with suggestions from several observations.