0bservation of the Geomagnetic Total Force at Kusatsu-Shirane Volcano
Ochi, K.
Abstract
After the small explosions at Kusatsu-Shirane Volcano in 1976，repeat measurement of the geomagnetic total force by proton-precession magnetometer has been carried out continuously every year at the observation points in and around the volcanic active regions. During the period from October 1982 to May 1984, the activity of Kusatsu-Shirane Volcano was enhanced in association with the frequent occurrence of volcanic earthquakes and five small steam explosions. In the present paper, the relationship between the volcanism and the long-term magnetic variation will be discussed based on the observation from 1976 to 1985. We confirm that the systematic spatial distribution of variations of the geomagnetic total force around the volcanic active regions could be interpreted by magnetization or demagnetization of the material beneath the volcanic active regions resulted from the volcanic thermal effect.
