松代地震群の地球電磁気学的調査(4)

A number of proton precession magnetometers have been set up over the Matsushiro earthquake area. One at Matsushiro indicated a definite increase in the total geomagnetic intensity and the other at Hoshina a decrease towards the end of August, 1966. These changes amount to some 5γ or a little larger. A marked change in the geomagnetic dip during a seven month\u27s period was found around Mt. Minakamiyama in the central area of the earthquake swarm. These local anomalous changes are unlikely to be accounted for by an intrusion of hot material. An alternative interpretation due to a piezo-magnetic effect is considered.松代地震は1966年4月頃に大きな活動期をむかえたが, 8月にはまたまた活発化している.この地震群を地球電磁気学的に研究するため,プロトン磁力計がつぎつぎに設置され, 10月初旬には長野県に7ヵ所になる予定で,かつてない精密観測といえよう.観測点はFig.1に示すように,つぎの各点である