Mechanical and electrical response due to fluid‐pressure equilibration following an earthquake

Abstract

The mechanical and electrical response in a uniform porous crust are determined following a shear dislocation (earthquake) on an internal slip surface. A uniform crust is studied because many exact analytical relations hold between the various response fields in this case. The initial stress field that is created immediately following the earthquake subsequently relaxes through time as the fluid pressure equilibrates by fluid flow. Maps of the electric field generated due to the fluid flow (electrokinetic coupling) are presented. Using conservative estimates of the various parameters involved, electric fields significantly larger than the diurnal (magnetotelluric) fields are generated. Quantitative results for how various components of the stress tensor change due to the fluid equilibration are also presented. The Coulomb stress can easily change by 100% (and more) in the months following an earthquake due to the fluid‐pressure equilibration.