Features of Historical Eruptions at Miyake-jima Volcano

Abstract

The old documents on the historical eruptions as well as the observational facts are precisely examined. Based on the carefull examinations, the typical features of Miyake-jima eruptions were clarified as follows : 1. Usually the eruptions started the flank of the main cone, without any clear precursors except in the activity of 1940. 2. In all cases, the earthquakes and rumblings became sensible only a few hours before the eruption in a small limited area where the eruption broke out. 3. The flank eruptions ended within a few days. 4. The Miyake-jima eruptions were frequently accompanied by post-eruption earthquake swarms. Occasionally these seismic activity caused damage to the houses and inhabitants of the island. 5. The flank eruption was sometimes followed by summit eruption which continued for a considerable period. In this case, post-eruption earthquake activity was not violent. 6. It seems that the occurrence of the eruptions of miyake-jima volcano in historical times were basically under the control of a periodicity of about 22 years.