Infrared thermography of the fumarole area in the active crater of the Aso volcano, Japan, using a consumer digital camera

Abstract

Thermal information of volcanoes is crucial for understanding their magmatic activity. In active volcanoes, the fumarole temperature is measured in order to monitor the magmatic activity. In this study, a consumer digital camera has been used as an infrared thermometer in order to obtain the infrared images for a fumarole area in the active crater of the Aso volcano, Japan; the temperature of the fumaroles that are more than a few centimeters in diameter can be estimated from the recorded images. The aperture value and the exposure time of the digital camera can be optimized manually, and clear images can be obtained in a wider temperature range of fumaroles by using the digital camera than by the consumer camcorder used in the previous study. The spatial resolution can also be chosen by changing the lens. The sensor of the digital cameras is sensitive to the near-infrared wavelengths of light, and the temperature estimation by using light of these wavelengths is robust against disturbances such as atmospheric absorption. The temperature, size, and spatial distribution of the fumaroles estimated by using this thermometer are considered to be more reliable than those measured by the dedicated thermometer used in the Aso volcano and the consumer camcorder used in the previous study. The thermometer used in this study is handy and cost-effective. Moreover, it has better temperature and spatial resolutions for monitoring high-temperature volcanic activity.