Study on the method of fault zone survey by use of in-situ hydrogen gas measurement

Kurosawa, Hideki; Ishimaru, Tsuneari ; Shimada, Koji   ; Niwa, Masakazu   ; Kosaka, Hideki*; Saito, Satoshi*; Ninomiya, Atsushi

Research on the influence of fault activity on deep geological environments contributes to the reliability of geological disposal systems for HLW. In this study, preliminary test shows that measured value within 1 hour after measurement start is supposed to include hydrogen gas generated by rock fracturing during the drilling of sampling holes and that stored in surrounding disturbed rocks, though the monitoring from a hand-drilled hole is effective for a rapid measurement. We investigated the concentration of hydrogen gas emitted from the Yamasaki fault zone, in southeast Japan. In our survey, the points where high concentrations of hydrogen gas emission was detected were unevenly distributed along the active fault, and in the southeast portion of the study area where small earthquakes frequently occurred.