SEISMIC OBSERVATION IN SHIMABARA PENINSULA : ON THE ACTIVITY OF VOLCANO UNZEN

Abstract

In November 1966, observation of micro-earthquakes was carried out in Shimabara Peninsula on the western part of Kyushu for investigating seismic activity beneath Volcano Unzen when it is considered to be in the period of quiescence. An earthquake swarm which is presumably of volcanic origin occurred in the same district for three days in July 1966. During our observational period an earthquake sequence just happened to be well observed although its source proved to be quite unexpectedly located. They were aftershocks of a felt earthquake on November 12, 1966. However, no seismic activity was detected from beneath the volcano in two weeks observation so far as the power of resolution of the present observational system goes.