中国地方におけるネットワークMT法観測(邦文)

概要

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Network MT (Magneto Telluric) observations were carried out in the Chugoku district in order to study the resistivity structure of the crust and the upper mantle beneath the south-western Japan arc. The electric field variations were measured using 69 dipoles in total, whose lengths were more than several kilometers. The electric field variation measured at almost all the dipoles showed a good correlation with eastward geomagnetic field variation. Geomagnetic field variation data at the Kakioka Geomagnetic Observatory (Japan Meteorological Agency) were used to obtain MT impedances. MT impedances were calculated at each triangular section formed by two dipoles; these consisted of one central station and two branch stations of NTT (Nippon Telegraph and Telephone Corporation). MT impedances, which can be used for model analysis, were determined at 18 triangular sections in the San'in area, the northern part of the Chugoku district, where the effect of artificial noise caused mainly by leakage current from electrical railwavs can be ignored.