有珠火山2000年噴火 : 赤外画像で探る金毘羅山火口群・西山火口群の活動関係(<特集>2000年有珠山噴火 (2))

概要

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Usu volcano, located in Hokkaido, Japan, erupted on 31 of March 2000. Phreato-magmatic eruptions occurred at two vent groupings-the Kompirayama and Nishiyama Craters-on the northwestern foot of the edifice. We observed the eruptive activity using infrared thermal camera imagery taken and broadcast by way of the Internet. Software was made to analyse temporal variations in the number of infrared image pixels showing thermal anomaly, these corresponding to the high temperature parts of the eruption plumes from each vent group. This measure acted as a proxy for the amount of eruptive material being ejected from the craters. Every few hours, the Nishiyama Craters were observed to greatly increase their activity levels for a few minutes from a low level, while the Kompirayama Craters generally stayed at a relatively high level. The two vent groups showed a negative relationship between their activity levels at a few tens of minutes time scale. Two theoretical models (a self stimulating compressive oscillation model and a self stimulating aquifer level oscillation model) were presented to explain the observed negative relationship between them.
2002-09-17