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 subsurfa ce structure around the MTL, we carried out the magnetotelluric soundi ngs and the geomagnetic depth soundings in the northeastern Shikoku di strict, southwest Japan. We estimated the resistivity model at the dep th from the surface to 10 km, which explains the observed apparent res istivities 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 reflectio n seismic result. The north dipping MTL cannot be created by just a pr esent strike slip motion. It requires that the horizontally compressiv e stress dominated in the early stage of the fault.