Hydrological Impact of Earthquakes on Reverse and Normal Faults: Results From Numerical Models

Abstract

I investigate earthquake‐induced hydrological signals related to poroelastic deformation, thermal pressurization, fault‐zone dilatancy and rupture of a pressurized reservoir at depth. This is performed using a two dimensional plane strain model that simulates ruptures on reverse and normal faults governed by rate‐and‐state friction coupled to elastic deformation and fluid flow along with spatio‐temporal evolution of temperature and fault‐zone permeability. The results show that whereas phenomena such as elastic deformation generate fluid pressure changes in the crust around faults, mechanisms such as shear heating and dilatancy drive localized fluid pressure perturbations on fault planes. The relaxation of fluid pressure anomalies is governed by the permeability, which varies with depth and on faults due to transient fracturing and healing. Strong increases in permeability on fault planes during rupture favor rapid fault‐parallel fluid flow during and immediately following earthquakes. In addition, fluid pressure perturbations disperse laterally and decay rapidly close to the surface whereas they remain localized and persist for far longer due to low permeabilities at depth. I conclude that fluid pressure perturbations and fluid flow in and around ruptured faults may result from a range of interacting processes that may operate to varying degrees at different depths, positions relative to a fault and tectonic regimes.