火山岩の磁化の圧力効果 : 地震予知への応用・その (2)

概要

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On the occasion of Matsushiro earthquake swarm, anomalous variations of the intensity of the geomagnetic field, ca. 10 gammas were observed in relation to occurrence of earthquakes with moderate magnitude. The authors conclude that such geomagnetic field variations may be explained on the basis of the changes of the magnetization of rock owing to changes in stress in the earth's crust. On the basis of the experimental results on piezomagnetism and rock mechanics of volcanic rocks including the dacite lava of Mt. Minakami in Matsushiro, it is shown that release of 0.1 kb compressional stress in rock within the earthquake volume can cause the observed anomalous changes in the geomagnetic field, as it can be concluded from aeromagnetic survey that the magnetization of the earthquake volume is of the order of 10^<-3> emu/cc.
1968-04-01