Anomalous geoelectric signals possibly related to the 2000 Mt. Usu eruption and 2003 Tokachi-Oki earthquakes

Telemetric observations of pulse-like geoelectric signals induced in a vertical buried dipole at Erimo in Hokkaido, Japan reveal the occurrence of anomalous signals associated with precursor activity to the 2000 Mt. Usu eruption and 2003 Tokachi-Oki earthquakes. The anomalous signals, at least 10 times stronger than the usual background level, are free of contamination due to meteorological or anthropological noise. These geoelectric signals are hypothesized to occur due to electrostatic coupling as a synergetic effect of thermal stimulated exoelectron emission and the release of gas trapped in rock at depth in the precursor stage of major activity.