Preseismic hydrogen gas anomalies caused by stress-corrosion process preceding earthquakes

摘要: Simultaneous monitoring of He, H2, Ar, N2, CH4 and Rn in gas bubbles groundwater from the 1,500 m deep Nagashima well active Yoro fault zone, central Japan, reveals that three microearthquakes with M=1.6–2.6 zone are accompanied preceded by increases as is a moderately large event M=5.4 same zone. All focal distances earthquakes within 25 km. No comparable anomalies were seen species other than H2. We suggest selective preseimic H2 geochemical signals earthquake nucleation process stress-corrosion mechanism. Aseismic slips preceding likely to have enhanced production mechanochemical reaction fractured rock surface water pre-existing planes conduits.