34.松代における地磁気異常変化

Geomagnetic observation by a proton precession magnetometer has been resumed at a station in the central area of the 1965-66 Matsushiro earthquake activity towards the end of 1969. The purpose of the present observation is to see whether geomagnetic changes occur or not in association with a water injection experiment into a bore hole about 2 km distant from the station. Although no marked changes exceeding a few gammas were observed in relation to the experiment, it is ascertained that an anomalous decrease in the total geomagnetic intensity amounting to some ten gammas relative to Kanozan Magnetic Observatory, about 180km distant from the station, had taken place during the past three years. The observation was made exactly at the same point as that during the violent seismic activity in 1965-66.|松代における深いボーリング孔への水圧入実験に伴なう変化を調べる目的で,皆神山南方のプロトン磁力計観測が再開された.1965-66年の地震活動が活発だった時期の観測点に設置された検出,コイル支持台は,そのままに放置されていたので,正確に同じ場所で観測を再開したことになる.観測の結果,水圧入実験に伴なう変化は検出されなかったが,最近3年間にこの観測点の地磁気全磁力が,鹿野山を規準とした場合,約10ガンマの減少を示したことがわかった