Numerical simulation of the electromagnetic fields variations under the formation of the fault rupture before earthquake

Abstract

A 2D geoelectric model of a heterogeneous geological medium has been developed taking into account the processes occurred in the geological subj ect of flexure type which transforms into an uplift-thrust structure as a result of deformations. The model is based on a hypothesis of the variation of electrical conductivity of geomaterials in the local area of the fault under subcritical stress-state conditions due to the geodynamical processes. In the shear stress maximum area, in the plane of fracture of the uplift-thrust type, a zone of increased fracturing is developed contributing to the essential decrease of electric resistance due to filling the fractures by fluid - so named «conductive split». A numerical simulation has demonstrated that when transiting from the quasi-stratllied model to a 2D model with the high-resistive shield a redistribution of the total current density in the medium is increased essentially due to the effect of the «conductive split», taking into account the assumed formation of the zone of fracturing. In this case, amplitude of the electromagnetic (EM) field for the longitudinal polarization increases far apart from the area of the «conductive split». The result obtained may be applied as a background for the development of the monitoring technique of the electromagnetic fields measured on a surface of the Earth far apart from the earthquake epicenter and directly over the fault for the controll ing of a level of the fault maturity for the occurrence of the seismic event.