Study on the generation mechanism of coseismic electric signals

An electromagnetic fault model, which considers the compensation of the piezoelectric effect and the dislocation theory of faults, is presented to deal with reported coseismic electric signals. Charges are assumed to be induced by the stress changes associated with an earthquake. The stress-induced charges are quantified by the charge density as a function of the polarization, which can be calculated using a piezoelectric model and an analytical solution of seismic stress. The theoretical charge distribution around the Nojima fault, which moved at the 1995 Kobe earthquake (M=7.2), was obtained. The coseismic electric field, consistent with that observed at the Kobe earthquake, was estimated as the field due to the charges which compensate the piezoelectric charges.