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

本研究的目的是通过分析泄漏电流矢量来研究地壳块体边界带的特征行为，而泄漏电流矢量通常被认为是自电位分析的噪声。通过比较池田站观测到的漏电流波形。除了有轨电车铁路和靠近铁路的北陆观察隧道外，这两个车站之间的地电特性可以估计。所得结果如下：1)在北陆观测隧道（HKJ）和池田站（TIJ）两个站点进行了观测。HKJ靠近铁路，TIJ位于Nukumi断裂带上。2)长期变化分析。在HKJ，自电位的面积变化表现为湿区较高，干区较低。在TIJ， Nukumi断层走向的垂直分量几乎稳定，并表现出年度变化。3)在HKJ和TIJ两个站点同时进行了1 Hz采样的漏电流观测。虽然TIJ的漏电流幅值比HKJ的小，但两者的波形相差不大。通过对漏电流波形的FFT分析，发现两个地点的频率成分没有显著差异。4)在TIJ处，只有垂直于断层走向的分量才能观测到不同类型的泄漏电流。这一现象可能涉及到对断层构造的一些建议。

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.