閉山した鉱山の廃坑を利用した自然電位変化の観測(第3部地殻活動に伴う電磁波放射の研究)

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Using tunnels and shafts in Ikuno mine, which was closed in 1974, we started in 1987 to observe seismic events and temporal change of 1) electric self-potential (Frequency<0.01 Hz), 2) apparent resistivity, 3) underground water level, 4) water seepage from tunnel wall and 5) γ ray intensity. The main purpose of our comprehensive observation is to discuss correlation between the observed data in such a stable circumstance as that without excavation, taking account of the continuous observation of crustal movement which have been carried out before the mine was closed. Since all tunnels and shafts below the underground water table filled up with water now, we expect to catch any behavior of rock body in response to any change of underground water and also any preseismic or postseismic effect. From the observation of about five years, we found that the seismic events (S-P time<0.3 s; M<0) still occur even now in the vicinity of mine. From our preliminary analysis, the secular change of electric self-potential (Frequency<0.01 Hz) seems to correlate to the activity of the seismic event in the mine. In order to discuss the characteristics of electric self-potential in wider frequency range, we started to observe temporal change of electric self-potential in renges of 1) 0.01〜0.1Hz, 2) 0.01〜500Hz and 3)1k〜9kHz in addition to the range less than 0.01 Hz.
独立行政法人防災科学技術研究所の論文
1993-03-29