Multi-signal studying of seismo-ionospheric interconnections using VLF OmniPAL receiver

ELF-VLF measurements aimed at studying seismo-ionospheric effects started at the University of Electro-Communications in Chofu, Tokyo from the beginning of 1997. This work is a further extension of the work of Hayakawa et al. (1996) in which the terminator minimum time method for the searching of earthquake precursors was proposed. The authors found an abnormal shift of the terminator minimum time in the diurnal dependencies of the Omega (Tsushima) VLF station just a few days before the Kobe earthquake (January 17, 1995) and repeated up to the day of the earthquake. In the present work we apply a new processing technique based on wavelet analysis to clarify the hypothesis about the interconnection between an intensification of planetary waves and seismic activity supposed in Hayakawa et al