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

Abstract

[1] 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.

Finite-difference modeling of the electroseismic logging in a fluid-saturated porous formation

“…Since these electrokinetic phenomena are correlated with the properties of the porous media and the porous fluid flow in the media, potential applications in geophysical exploration and earthquake precursor monitoring were experimentally studied (see e.g. [2][3][4][5][6][7]). …”

Three-Dimensional Finite-Difference Time-Domain Computation of the Seismoelectric Field Generated by a Slipping Fault

“…The EM fields can be especially strong near the free-surface and have high attenuation along the depth because of the slow compressional wave, which is converted at the surface and has high attenuation under low frequencies (Pride et al, 2004). Thus local grid refinement should be applied near the surface in order to simulate the high attenuation of the EM fields.…”

“…The slow compressional wave under very low frequencies can be considered as a diffusion phenomenon and can be simulated by solving the diffusion equations, as done by Pride et al (2004) by considering the fast compressional wave as a quasi-static field. We apply their ideas into our FDTD algorithm, without assuming that the fast compressional wave is a quasi-static field.…”

Origin of transient self‐potential signals associated with very long period seismic pulses observed during the 2000 activity of Miyakejima volcano

“…The zero‐pressure surface condition on a uniform half space results in zero horizontal component of the electric field at the ground surface. Pride et al [] argued that the zero‐pressure, open‐pore boundary is appropriate for their study because an impermeable layer is outside their scope of studying a uniform crust. In the present study, however, the observation data do show nonzero horizontal components.…”