Reflections on the electrostatic characteristics of direct current in an anisotropic medium

Abstract

Electrical anisotropy is a common property of rocks. The theoretical behaviour of the survey results of direct current methods is considerably more complicated in an anisotropic than in an isotropic model. The physical causes of the formal properties of anisotropy are examined by analysing the charge distribution of a point current source in an anisotropic space. It is shown that the charge density generated by anisotropy around the point source is inversely proportional to the third power of the distance from the source point. The charge is negative in the environment of the long principal axes of anisotropy but positive around the short principal axes. The total charge outside the source point is zero. The charge distribution stretches the equipotential surfaces into ellipsoids and bends the lines of force.