Volume 136 (2016) Issue 5 Pages 310-314
In order to verify the seismo-electric phenomena before large earthquakes (EQs), stress-stimulated charges (SSCs) in the lithosphere were assumed and the frequency characteristic was evaluated for the electromagnetic field caused by the SSCs, considering a charge generation coefficient and resistivity in crust. Time variation of SSCs was dependent on the stress-changing rate and the degree of dielectric relaxation. Possible electromagnetic spectra due to apparent charges were obtained by the linear system analysis. Because of the low resistivity in ordinary crust, SSCs after a short stress-changing event were quickly recombined and would not contribute much to EQ precursor phenomena. On the other hand, preseismic seismo-electric phenomena such as GPSTEC anomalies are known to last as long as 40 minutes. In order to achieve such long lasting electromagnetic phenomena before an EQ, the resistivity of the interested area should be enough high or the stress changing in crust should last continuously enough long. We can also assume continual stress-changing events at multi-spots around the fault zone which lasting several tens of minutes before large EQs.