The electrical structure across the Median Tectonic Line in east Shikoku, southwest Japan

The Median Tectonic Line (MTL) is one of the longest tectonic lines in Japan with the lateral movement. In order to investigate the subsurface structure around the MTL, we carried out the magnetotelluric soundings and the geomagnetic depth soundings in the northeastern Shikoku district, southwest Japan. We estimated the resistivity model at the depth from the surface to 10 km, which explains the observed apparent resistivities and phases. The most remarkable feature of the resistivity model is that the subsurface extension of the MTL has a north dip down to 5 km depth. This dipping interface also corresponds to a reflection seismic result. The north dipping MTL cannot be created by just a present strike slip motion. It requires that the horizontally compressive stress dominated in the early stage of the fault.