Remote Sensing in Geothermal Investigation

Abstract

Remote sensing study and application in the Geological Survey have twenty years of history back to 1965. They have mostly been done as a part of research work related to geothermal investigation. Among them, three subjects are put lights in this article ; they are, 1) early date case history on aerial thermography, 2) a volcano-geologic study initiated from Landsat image observation, and 3) remote sensing application in the Hohi geothermal area. Aerial thermography represents one of the earliest remote sensing stud y in Japan. Other two are the example that the aspect given by remote sensing investigation has b een taken into account in the following survey including drilling.
Research on aerial thermography was started in 1965 and it included the co -research with the Nippon Electric Company on the construction of airborne thermal infrared scanners.The technique was used for regional geothermal survey in 1970s and recent research aims at the quantitative use of the data for more detailed temperature mapping.
A large circular feature with 15 km in diameter, newly found in the Landsat image of northern Honshu, has been surveyed since 1978 in view from both volcano -geology and geothermal resources. It was identified to be a half concealed Plio-Pleistocene caldera and named Okiura Caldera. The result of drilling done mostly during 1981 and 1982 for geo-thermal development indicates that the higher temperature portion lies inside the caldera suggesting the influence of magma resurgency.
A big national geothermal survey is being conducted in the Hohi geothermal area, north central Kyushu and several remote sensing data were used for the survey. These data include Landsat, airborne SAR, and aerial thermograph as well as conventional aerial photograph. Examples of quantitative evaluation of the aerial thermoraph and field evaluation of a long lineament extracted from the SAR image are introduced in the article. An attempt for structural analysis using digitally processed Landsat data and geophysical data such as gravity and aeromagnetic data is being attempted in the Hohi geothermal area.