It is observed that seismic waves generate electromagnetic variations. The excitation mechanisms have been analyzed and formulated by many researchers. Three mechanisms have been mainly considered; stress effects for physical properties of rocks such as the piezoelectricity and the piezomagnetic effects, the electromagnetic induction due to the oscillation in the geomagnetic field, and the electrokinetic phenomena in pore fluids. While the stress effects and the electrokinetic phenomena take place in the crust, the induction process functions in various regions of the earth as the crust, the oceans, and the ionosphere. The characteristics of the electromagnetic signals produced with these mechanisms are also reviewed. It is expected that the electromagnetic signals derived from seismic waves are used to investigate the dynamics and the structures of the earth and planets.
