Chapter 20 – Electric Polarization Related to Defects and Transmission of the Related Signals

This chapter describes electric polarization related to defects and transmission of the related signals. It also reviews basic concepts that explain the origin of the polarization (or depolarization) effects associated with defects in solids. Because the emitted electric currents travel through the conductive Earth crust, therefore it is important to study the macroscopic Maxwell equations for a conductive body. Numerical results have been obtained in a variety of thin-sheet model calculations by means of the numerical solution of Maxwell's equations. Electric signals are emitted well before fracture from rocks under a gradually increasing stress. These signals, when emitted in the Earth, should follow paths of reduced resistivity. Analytical and numerical solutions of Maxwell equations coincide in concluding that such signals emitted from the focal area give detectable electric field values at distances of r ≈100 km or so. These electric signals are detectable on the Earth's surface at certain regions only, which explains the "selectivity effect" reported long ago by VAN observations.