Radon concentration distributions in shallow and deep groundwater around the Tachikawa fault zone.
Groundwater radon concentrations around the Tachikawa fault zone were surveyed. The radon concentrations in shallow groundwater samples around the Tachikawa fault segment are comparable to previous studies. The characteristics of the radon concentrations on both sides of the segment are considered to have changed in response to the decrease in groundwater recharge caused by urbanization on the eastern side of the segment. The radon concentrations in deep groundwater samples collected around the Naguri and the Tachikawa fault segments are the same as those of shallow groundwater samples. However, the radon concentrations in deep groundwater samples collected from the bedrock beside the Naguri and Tachikawa fault segments are markedly higher than the radon concentrations expected from the geology on the Kanto plane. This disparity can be explained by the development of fracture zones spreading on both sides of the two segments. The radon concentration distribution for deep groundwater samples from the Naguri and the Tachikawa fault segments suggests that a fault exists even at the southern part of the Tachikawa fault line.
Geochemical Research Center, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan. Electronic address: eqpred@gmail.com.
Fumiaki
F
Tsunomori
Collage of Liberal Arts, International Christian University, 3-10-2 Osawa, Mitaka, Tokyo 181-8585, Japan.
Tomoya
T
Shimodate
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
Tomoki
T
Ide
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
Hidemi
H
Tanaka
D005844:Geology; D060587:Groundwater / Q000737:chemistry*; D007564:Japan; D011834:Radiation Monitoring; D011886:Radon / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
D014875:Water Pollutants, Radioactive; D011886:Radon
Fracture zone; Groundwater; Radon concentration; Tachikawa fault