Synthetic study of precursory phenomena of the M7.2 Hyogo-ken Nanbu earthquake

Abstract Many seismic precursory phenomena in the ionosphere, atmosphere, and underground water were observed by professional and amateur people before the M7.2 Hyogo-ken Nanbu earthquake of January 17, 1995. The seismic precursory phenomena are a tornado-type seismic cloud ascending over Nojima fault near the epicenter, anomalous foEs increases above 7 MHz observed at epicentral distances within about 500 km, anomalous ELF–VLF radio noises from lightning discharges, anomalous extensions of the characteristic terminator times toward darker local times in phase variations of Omega 10.2 kHz waves passing about 70 km north of the epicenter, radon concentration increases in the atmosphere on a fault in Kobe and those in the underground water near a subsurface fault in Nishinomiya, and radon ion density increases in Okayama about 200 km west of the epicenter. We study synthetically relations among these seismic precursory phenomena in the ionosphere, atmosphere, and underground water before this earthquake onset. Then, we propose desirable observations for warning great earthquakes.