Investigation of the Characteristic Behaviors of the Crustal Block Boundary Deduced from Leakage Current Vectors

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The object of this study is to investigate the characteristic behaviors of the crustal block boundary zone by analysing the leakage current vectors which are usually considered to be noises for self-potential analyzes. By comparing the waveformes of the leakage current observedat Ikeda station. apart from the street-car railway, with those at Hokuriku observation tunnel, near the railway, the geoelectric characteristics between those two stations can be estimated.Obtained results are as follows ;1)Observation have been carried out at two sites, Hokuriku observation tunnel (HKJ) and Ikeda station (TIJ). HKJ is closed to the railway and TIJ is on the Nukumi fault zone.2)Long-term variations were analyzed. At HKJ, areal variation of self-potential showed relatively high level in wet area and low in dry area. At TIJ, perpendicular components to the Nukumi fault strike have been almost stable and showed annual variations.3)Leakage current observation of 1 Hz sampling was carried out simultaneously at both HKJ and TIJ sites. Although the amplitudes of leakage current at TIJ were smaller than those of HKJ, those waveforms of both sites did not differ so much. By FFT analyzes of leakage current waveforms, remarkable differences in frequency components were not recognized in both sites.4)Some different types of leakage current were observed only by the components which are perpendicular to the fault strike at TIJ.This phenomenon might involve some suggestions about the fault structure.