漏洩電流の性質について(1)

Abstract

Preferred orientation surveys of telluric currents which are leaked from electric railways are carried out around Obaku ground to estimate precise position of the Obaku fault which is covered with sedimentary layers. The method is based on some characteristics of leaking currents which tend to flow with preferred orientations depending upon electrical resistivity structures beneath observation sites. The result shows the fault line is not clearly identified because data are not sufficient although one of candidates is estimated to run along east side of the ground. This is rather consistent with the result found from ar-ray survey carried out by Mino and Takeuchi.Temporal changes of the preferred orientation on the Obaku fault are also precisely examined to detect temporal changes of resistivity around the Obaku fault in relation to some crustal activities such as earthquake occurrences. We find that day to day fluctuations of the preferred orientation is as small as several degrees although the direction is a little fluctuated with precipitations.