Infrared and hyperspectral remote sensing of Earth degassing

Abstract

Geodynamical processes often cause degassing at the Earth surface. There the geogas emanates via mineral springs, water mofettes, or dry mofettes. It is assumed that the emerging gas influences the temperature of the springs¡¦ or mofettes¡¦ water, respectively the surface temperature of the soil at and around the dry gas vents. This causes a thermal anomaly in comparison to the close vicinity. If the anomaly is sufficiently pronounced with respect to the temperature difference ƒ´T to the vicinity and to the area A influenced by the effect it can be extracted from remotely acquired infrared images. Investigations have commenced to investigate whether the effect can be utilised to detect gas emanations through airborne infrared imaging measurements. In such a way gas vents/springs could be mapped and monitored within large areas and short times. As a first approach compressed air was lead into the ground and released in some depth via a metal lance. The thermal effect at the surface was observed by a thermovision camera over several hours under varying meteorological conditions. Temperature in the depth was measured using contact thermometers for comparison. In addition simulations were performed to determine the temperature difference ƒ´T and the area A of the thermal anomaly required for detection by typical remote sensing instrumentation. Results of measurements and simulations will be presented. The investigations are aiming at studies to be performed in the Western Bohemia (Czech Republic) earthquake swarm region where especially CO2 of magmatic origin from European Subcontinental Mantle (ESCM) emanates.