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| | Abstract | | AIST has equipped sixteen groundwater observation stations with measuring instruments between the Tokai and the Shikoku district to predict the Tonankai/Nankai earthquake. Water gauge, strain gauge and seismometer etc. were installed in bore holes. Subsurface structure survey, well logging and stress measurement etc. were also conducted at each station. The latest subsurface structure survey was conducted at Niihama station in Ehime Prefecture. The survey line is 10 km long, runs near the station and crosses several active faults of the Median Tectonic Line. The Ishizuchi fault, terrain boundary between the Sambagawa metamorphic rocks and the Izumi group, is clearly imaged and it dips northward in the seismic section. The Izumi group is not recognized well and the Okamura fault is interpreted on the basis of discontinuities of reflectors. |
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