松代地震群の地球電磁気学的調査 (3)

Geomagnetic observations have been continued over the Matsushiro area since the middle of October, 1965. The results of observations during the period from February to April are reported. Five-day means of the total intensity observed at the centre of the seismic area revealed small fluctuations amounting to approximately ±2γ. As a result of magnetic dip surveys repeated with an interval of two months, it has turned out that there are localities where magnetic inclination changed more than 1\u27. Magnetic dip surveys were extended over the Toyono-Nakano-Susaka area in association with an unusual upheaval of land observed. Changes of the same amount as those in the Matsushiro area are indicated there. No clear relation between the geomagnetic changes and the seismic activities has been obtained.松代における全磁力の測定はその後も続けられ, 2月9日以来B測点では午前1時より2分間隔で6回自動的に測定するような装置に切りかえた.これは夜間の測定が昼間の測定よりよいデータを供するからである.この測定値と鹿野山の同時刻の値との差の5日平均の変動は±2γ程度のものであるが,これと地震活動との直接的な関係は明らかでない