Detection of Geothermal Anomalies and Evaluating Land Surface Temperature in Northern Abaya Geothermal Field, Main Ethiopian Rift
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Date
2020-09-02
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Addis Ababa University
Abstract
Land Surface Temperature (LST), which is a radiative skin temperature of a given area, depends on several factors and physical parameters indicating that a onetime satellite image analysis will not be enough to identify areas with geothermal potential. Given the difficulty associated with surface temperature over wider areas, its characterization, distribution and temporal evolution, therefore, necessitates measurements with thorough spatial and temporal samplings. In the present thesis, a multi temporal Thermal infrared (TIR) remote sensing data (2000-2019 in two years interval) from the Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) and Landsat has been used to detect geothermal areas and evaluate the LST of the northern Lake Abaya geothermal prospect of the southern Main Ethiopian Rift (MER). The study uses the single channel algorithm to derive LSTs and compare the result with borehole data from different literatures.
The result shows that the mean LST is highest in 2003 (320.1 K) and lowest in 2019 (303.1 K). The change in mean LST was between –9 K to 13 K. This LST results from ASTER images were validated with ASTER LST products and show more than 70% correlations. The derived LSTs from the nine images were compared with the borehole data. LSTs of the year 2003 have been much closer to the actual temperature value from borehole data. The geothermal anomaly areas were validated with the existed field data (19 sites). Fifteen sites fall in the identified geothermal anomaly areas, which is 79 % of the total. The result of correlation between time and LST values in known geothermal activity sites shows no correlation (less than 0.5) except one site, which is Boramitta (0.54). This shows that the LST is time invariant which goes well with the fact that there shouldn‘t be any significant change of LST in geothermal anomalous areas.
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Land Surface Temperature (Lst), Geothermal Anomaly, Main Ethiopian Rift (Mer), Thermal Infrared (Tir)