Three-dimensional distribution and hydrogeological properties of the Omagari fault in the Horonobe area, northern Hokkaido, Japan

Ishii, Eiichi; Yasue, Kenichi; Tanaka, Takenobu*; Tsukui, Rota; Matsuo, Koichi*; Sugiyama, Kazutoshi*; Matsuo, Shigeaki*

Chishitsugaku Zasshi, 112(5), p.301 - 314, 2006/05

https://doi.org/10.5575/geosoc.112.301

Fault zones have significant influences on ground water flow. It is important to understand the characteristics of fault zones for hydrogeological modeling. We investigated the hydrogeological property and the geological structure of the fault in Neogene siliceous sedimentary rocks of northern Hokkaido, using geological mappings, reflection seismic surveys, and audio-frequency magneto telluric surveys. The result of description at a fault outcrop suggests that the Omagari Fault is a fault zone of about 120 m width that consists of mainly damage zone and that is a permeable structure without the strong anisotropy in permeability. In addition, the result of magneto telluric surveys shows high-resistivity zones having a flower structure, and one of the high-resistivity zones corresponds to the position of the Omagari fault inferred from the results of the reflection seismic surveys and of the borehole investigations. These high resistivity zones overlap with the low saline concentration zones, and the overlapping suggests the infiltration of the fresh water from the surface into the deeper part through the Omagari Fault as permeable structures. Based on these results and on study of the hydrogeological property, the geological structure, and petrological characteristics in and around the fault, it seems that the fault is a sinistral oblique-slip fault with eastside uplift sense that is formed after late Pliocene to early Pleistocene, but the possibility of the previous activity needs to research, and that the fault is over-stepping at the surface and is converging in deep underground like a flower structure shape.

Developing a remote monitoring system using ACROSS in Horonobe Underground Research Laboratory

JNC, 1)*; Niizato, Tadafumi; Aoki, Kazuhiro; ;

International workshop on "Active Monitoring in the Solid Earth Geophysics", 0 Pages, 2004/07

Japan Nuclear Cycle Development Institute (JNC) is developing a remote monitoring system using seismic and electromagnetic ACROSS (Accurately Controlled Routinely Operated Signal System) in the Horonobe Underground Research Laboratory (URL). The Horonobe URL project is devoted to the technological development for a safe geological disposal of high level radioactive wastes over a 20-year period from March 2001 in Horonobe-cho in northern Hokkaido, Japan. The purpose of installing a remote monitoring system is to monitor changes in the geological environment before, during and after the construction of an URL facility. The source and receiver system of electromagnetic ACROSS and the receivers of a seismic ACROSS will be installed in the fiscal year 2004, while the source of the seismic ACROSS will be transported from Tono Geoscience Center in 2005.

Seismic Reflection Survey for Tono Regional Hydrogeological Study Project

Tsukui, Rota*; Kawanaka, Taku*; Ota, Yoichi*

JNC TJ7440 2005-075, 257 Pages, 2003/03

JNC-TJ7440-2005-075.PDF:57.05MB

no abstracts in English

The Horonobe Underground Research Laboratory project; Outline and progress of development of remote monitoring system (ACROSS)

Ohara, Hidefumi; Tsukui, Rota; Kunitomo, Takahiro; Nakajima, Takahiro; Niizato, Tadafumi; Aoki, Kazuhiro; Shigeta, Naotaka; Kumazawa, Mineo

no journal, , 

Japan Atomic Energy Agency (JAEA) is developing a remote monitoring system using seismic and electromagnetic ACROSS(Accurately Controlled Routinely Operated Signal System), to monitor changes in the geological environment. ACROSS has been researched and developed in Tono Geoscience Center for 9 years, and we introduce it to the Horonobe Underground Research Laboratory (URL) project. The Horonobe URL project is devoted to the technological development over 20-years from March 2001 for a safe geological disposal of high level radioactive wastes in Horonobe-cho in northern Hokkaido, Japan. We install the monitoring system before the shaft excavation, and collect data before, during and after the excavation, in order to permit assessment of the system's reliability. The source and receivers of electromagnetic ACROSS were installed in the winter before last, and we are carrying out the test of the system. In last December, the source and receivers of a seismic ACROSS were installed in Horonobe. Then we are going to examine the practicability of ACROSS.