Subterranean electrical structure of Kozu-shima volcanic island, Japan.

Following the electric current injection experiment carried out in 2009, a VLF-MT (Very Low Frequency Magnetotelluric) survey has been conducted in Kozu-shima Island to obtain further information on the subterranean electrical structure that might help understanding the results of our monitoring of geoelectric potentials. A number of VAN-type pre-seismic geoelectric potential anomalies were observed in 1997-2000, even showing a remarkable "Selectivity". However, similar pre-seismic anomalies were not observed during the Izu-Island volcano-seismic swarm 2000.