松代町・皆神山岩体の磁性 : 地震予知への応用・その (1)
1968 年 13 巻 1 号 p. 1-11
詳細
1968 年 13 巻 1 号 p. 1-11
Results of the measurements of magnetic properties of dacitic rocks collected from a lava dome, Mt. Minakami (Matsushiro, Nagano prefecture) are presented. The results suggest that the geomagnetic anomalies covering Mt. Minakami and its southwest area are caused mainly by stable remanent magnetization of ferromagnetic minerals with very fine grain sizes in the rocks. In an attempt to elucidate the geomagnetic field variations which might be accompanied by the earthquakes in the anomalous area, the pressure effects on the remanent magnetization of rock samples are examined. Irreversible decrease in the remanent magnetization of rocks is within 3 %/kb up to 5 kb of compressional stress.
