Identification of pathways for hydrogen gas migration in fault zones with a discontinuous, heterogeneous permeability structure and the relationship to particle size distribution of fault materials

Niwa, Masakazu   ; Kurosawa, Hideki; Shimada, Koji   ; Ishimaru, Tsuneari ; Kosaka, Hideki*

Previous studies have reported that high concentrations of H gas are released from active fault zones. Experimental studies suggest that the H gas is derived from the reaction of water with free radicals formed when silicate minerals are fractured at hypocenter depths during fault activities. Based on the H gas measurements and the particle size distribution analyses, the deep-seated H gas is considered to have migrated in permeable damage zones mostly by advection with groundwater. Multipoint H gas measurement will be effective in delineating qualitatively, variations in permeability of regional structures.