阿蘇火山の波形の似た火山性地震

Abstract

Volcanic earthquakes near the active crater of Naka-dake, Volcano Aso, can be dividedinto two kinds, high frequency events and low frequency ones. High frequency events aredominated by signals with higher frequency than 10 Hz and occur in the depth range, 0-3km below sea level. Low frequency events are located in 2 km range of shallow depth directlybeneath the crater bottom, 1.2 km above sea level.The low frequency events appeared mostly as earthquake swarm. The similar eventshaving similar waveforms were recognized among the low frequency events. In a series ofseismic activity, the similar event activity occurred at first and then was accompanied withnon-similar event activity.Ten groups of the similar events were classified in 1984-1986. It is supposed that thesimilar events are associated with the movement of magmatic material in the volcanic vent.