比抵抗変化計のテレメーターシステム
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概要
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A continuous high sensitivity observation of apparent ground resistivity was first started at the Aburatsubo Crustal Movement Observatory (139°37'E, 35°09'N), Kanagawa Prefecture, about 60 km south of Tokyo on May 14, 1968. The initial intention was to observe the crustal movement reflected on the resistivity variation. The initial resistivity observation system consisted of the following sections : 1) four graphite electrodes buried in the floor ground of a small vault near the shoreline of the Aburatsubo Bay, with 1.6 m distance in N81°W direction, 2) a 67 Hz type resistivity variometer and 3) two sets of aerial cables which connect the electrodes and the resistivity variometer. The apparent resistivity change in response to the tidal loading of the ground has been continuously recorded with a sensitivity as high as 102 compared with the earth'strain at Aburatsubo. Unexpectedly, on every occurrence of the remarkable earthquakes in the vicinity of Japan, the resistivity variation has been observed. Up to the present, the author observed 50 remarkable coseismic resistivity changes most of which are accompanied by the precursory resistivity change the order of hours preceding to the respective earth- quakes. From September 2, 1978, the prototype vacuum tube apparatus was replaced by an IC type two component resistivity variometer which is capable of a future coupling with a telemeter system without interfering with observation under continuous operation. On February 14, 1980, real time continuous telemetering of the resistivity variation to the author's laboratory at the Earthquake Research Institute was started through D1 service line of Nippon Telephone and Telegram Agency (NTT) The telemeter system is a low-speed, 50 bits/sec, one-way, PCM telemeter equipment with four 8 bits channels. The first telemetered coseismic resistivity change at Aburatsubo was of an earth- quake of magnitude 5.9 on March, 1980. The agreement of the directly recorded resistivity change at Aburatsubo and the telemetered record at the Earthquake Research Institute is quite satisfactory. The coseismic resistivity change for the earthquake of magnitude 6.7 on June 29, 1980 is also shown at Aburatsubo.
- 1981-03-07