岐阜県神岡町二十五山での発破の際の電磁気観測

概要

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Electric and magnetic features of the impulsive waves were measured at quarry explosion. The measurement of the electric self-potential was made by the four electrodes arranged in the northeast line through the explosion point. The distance of the each electrode from the explosion point ranges from 40m to 110m. The explosion was induced by 11.4 kg dynamite and 325 kg ANFO placed at the ground surface. Twice explosions with the time intrerval of 25 msec were set up and practiced. Extinct changes in electric self-potential were observed in two successive times by plural electrode couples. These changes in self-potential correspond exactly to twice explosions, respectively. There is a possibility that the first change in self-potential may have been caused by the ignition current of the detonators used at the starting of the explosion. The analysis shows, however, that the second change in self-potential had no relation to the ignition current. When the propagation speed of the change in self-potential was calculated using the time between the explosion time and the time of change in self-potential, the speed was estimated to be more than 100 km/sec. No clear electromagnetic radiation (VLF) was observed at the distance of 80m from the explosion point.
独立行政法人防災科学技術研究所の論文
1995-03-31