Japan Geoscience Union Meeting 2016

Presentation information


Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG60] Crustal fluids and deformation

Tue. May 24, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Naoji Koizumi(School of Environmental Science,the University of Shiga Prefecture), Koji Umeda(Tono Geoscience Center,Japan Atomic Energy Agency), Norio Matsumoto(Tectono-Hydrology Research Group, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST)), Hidemi Tanaka(School of Science, The University of Tokyo), Kohei Kazahaya(Geological Survey of Japan, AIST), Fumiaki Tsunomori(Geochemical Research Center, Graduate School of Science, University of Tokyo)

5:15 PM - 6:30 PM

[SCG60-P03] Hydraulic properties, water chemistry and gas composition at Hongu observatory, Wakayama Prefecture

*Norio Matsumoto1, Tsutomu Sato1, Akinobu Miyakoshi1, Noritoshi Morikawa1, Masaaki Takahashi1, Hitoshi Tsukamoto1, Kohei Kazahaya1 (1.Institute of Earthquake and Volcano Geology, National Institute of Advanced Industrial Science and Technology (AIST))

Keywords:hydraulic property, water chemistry, gas composition, deep well

In order to explore potential sites for in-situ continuous 3He/4He gas mass spectrometer which is under development, we performed temperature and electric conductivity logging and hydraulic tests at a 1000 m well at the Hongu observatory. We also collected groundwater and gas samples from the well after the hydraulic tests. There are several reasons why we selected the Hongu observatory as the potential site: (i) High 3He/4He ratio were observed in the hot springs near the Hongu observatory; (ii) Several ancient texts reported that discharge of hot spring at the Hongu area were stopped in response to past Tonankai or Nankai earthquakes, and (iii) we have been observing groundwater, crustal deformation and seismic data near the Hongu observatory to detect non-volucanic tremors and short-term slow slip events occurring at plate boundary directly underneath the Hongu area. As a result, we obtain medium transmissivity of the aquifer (2.0 - 2.8 x 10-5 m2/s), high 3He/4He ratio (4.69 Ra) in the gas sample and similar chemical composition of the sampled water to the surrounding hot springs.