The Measurement of Thermal Areas in the Nakadake Crater of Asosan, by an Infrared Radiation Thermometer

Abstract

The authors carried out temperature measurement of the ground surface at the Nakadake Crater of Asosan, used an infrared radiation thermometer, and compared the twice observation results at the calm period and the eruption time of the volcano. High temperature zones in the crater bottom and the crater wall were situated at the north half part of the Nakadake Crater, and anomalous high temperature zones at the eruption time extended about ten times as large as that of the calm period. Furthermore, these anomalous high temperature values at the eruption time were 10℃ to 15℃ higher than that of the calm period. These suggest that some thermally anomalous areas in the crater may change their thermal characteristics before or at the future eruptions. The thermal infrared surveys are very useful to volcano observation for the monitoring of some potentially hazardous crater, and these surveys can be done with safety and quickness.