Model constraints on infiltration of surface-derived fluid deep into the brittle crust: numerical results

Fluid is driven downward along a fault either due to gradients in hydraulic head arising from topography or due to dilation on the fault during earthquakes (seismic pumping).   Results show that both forcing scenarios are equally capable of driving surface-derived fluid to the base of faults at 10 km depth in several tens of thousands of years.

Downward flow of cold fluid occurs almost exclusively during and shortly after earthquakes, while during the remaining portion of the seismic cycle fluids remain relatively stationary while they undergo thermal relaxation (i.e., heating). Rapid downward flow is favoured by a large coseismic permeability, long permeability healing time scale, and large coseismic dilatancy or high topographic relief above the fault at the surface.