Journal of Natural Disaster Science

INSTALLATION OF PENETRATOR-TYPE THERMOMETERS AND BLASTMETERS FOR DETECTING PYROCLASTIC SURGES DURING ERUPTIONS OF UNZEN VOLCANO, KYUSHU, JAPAN

Keiko SUZUKI-KAMATA
Kazuyoshi SANGEN
Department of Earth Sciences, Faculty of Science, Kobe University
Hiroki KAMATA
Osaka Office, Geological Survey of Japan
Hiromitsu TANIGUCHI
Science Education Institute of Osaka Prefecture
and
Setsuya NAKADA
Department of Earth and Planetary Sciences, Kyushu University

(Received 12 August 1992 and in revised form 23 February 1993)

Abstract

Pyroclastic flow is one of the most destructive eruptive phenomena and has kept scientists from making direct measurements of its physical properties. We constructed two types of penetrators to measure the temperature, over pressure and particle velocity of a pyroclastic surge accompanied by a pyroclastic-flow eruption. The penetrator-type thermometer measures temperature and duration of a pyroclastic surge based on the change in state of several kinds of metals and thermodyes which melt at specific temperatures during volcanic events. The penetrator-type blastmeter estimates the explosion energy and particle velocity of a pyroclastic surge on the basis of the deformation of a thin metal plate. A helicopter of the Japanese Self Defense Force was used to drop 12 penetrators from a height of 30-45 m at 5 points on Unzen Volcano in Kyushu, Japan, most of which landed erect. Measurements made with this type of penetrator enable us to obtain certain physical properties of pyroclastic surges in dangerous areas during explosive eruptions.

Key words

penetrator-type thermometer, penetrator-type blastmeter, pyroclastic surge, Unzen Volcano