Primary and crack-induced anisotropy of electric resistivity before earthquakes

Electric resistivity of a medium with an oriented system of open cracks that undergo changes when under stress is simulated numerically. The concentration of cracks - their quantity and volume - varies, along with stress rise and energy release. The same may be true for the proper resistivity of a material inside cracks. The crack system is treated as 3-dimensional, anisotropic, although homogeneous from the observer\'s point of view. Also, a second source of electric anisotropy of the medium, its primary anisotropy is taken into account; it is independent of cracks and unchanging. Geometrical modelling reveals the possible role of rock anisotropy in monitoring and for prospecting. Attempts to interpret experimental results are also given.