Geomagnetic Observation around the Volcanos Kirishima
Nagai, M. & Nagano, T.
Abstract
After an earthquake swarm which occurred in the area of Kakuto caldera, many cases has been founded in the past that shallow and small volcanic earthquakes swarmed at the vicinity of Shimmoe-dake or that volcanic eruptions occurred at the Ohachi crater of Takachiho-mine in the southeast part of Kirishima volcanic zone.
After the recent Ebino earthquake swarm, shallow volcanic earthquakes swarmed at the vicinity of Shimmoe-dake in March 7th and 8th, 1968 and soon came to an end. Moreover, the activity of earthquakes was switched over to the south-east, and volcanic earthquakes swarmed at Naka-dake in March 1969 with volcanic tremors too. After a time, the activity of earthquakes was shifted more and more to the south-east from Naka-dake to Takachiho-mine in October, and the volcanic earthquake swarm was concentrated at the vicinity of Ohachi crater in December 1969.
ln order to survey the relation between geomagnetic variation and earthquake swarm or volcanic activity, Dip observations were carried out around the volcano Kirishima in March 16-27, 1968 and October 27-28, 1971.
It was ascertained from these observations in the active and calm period of earthquake swarm that the Dip variation was about 1-2' at the station near the Ohachi crater of Takachiho-mine which was caused by the upheaval of magma, though there was no volcanic eruptions.
