Seismic Reflection Survey across the Median Tectonic Line and its 3-D Structure

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15.5-Km-long seismic reflection survey was done by two "Vibroseis" machines across the Median Tectonic Line(MTL),east Shikoku,from February to March in 1992.Accompanied with this seismic survey,gravity,magnetotelluric(MT),magnetic surveys were also made along the seismic survey line.The results from the surveys clearly show that MTL dips northward at 30 to 40 degrees from the ground to about 5.5 km deep.The deeper-than-5.5-km part of MTL has not been found in the reflection profile,because signals from the deeper are too weak.Before our survey, most geologists believe that MTL must be vertical from the shallower to deeper. Therefore our results are revolutionary and they require the re-examination of formative process of MTL.