静岡県相良町の地殻傾斜連続観測点における比抵抗探査

Abstract

In order to detect precursory crustal movements of the Tokai earthquake, Shizuoka Prefectural Government installed a water-tube tiltmeter, at Sagara, central Japan. Since June 1983, crustal tilting has been continuously observed by Shizuoka University. The secular trend obtained by means of this tiltmeter has shown always northwestward. On the other hand, the results of repeated levelings in this region show tilting southeastward. In order to account for this inharmonic tilting, we propose a model of the active folding, associated with the subduction of the Philippine Sea plate, under the Sagara station.As one of the trials to confirm this model, we carried out electrical resistivity surveys using the Wenner method in December 1994 at Sagara station. 5 profiles crossing the base line of the water-tube tiltmeter were conducted. The results show that it is difficult to support the existence of the fold structure.