LINEAMENT EXTRACTION AND ANALYSIS USING REMOTE SENSING IN NORD GHOUBBET GEOTHERMAL FIELD, DJIBOUTI

Abstract

Remote sensing is useful at the pre-feasibility stages of geothermal exploration. Lineament study is one of the most important assets for geothermal resource exploration. Several surface manifestations, in particular, fumaroles occur in Nord-Ghoubbet geothermal field and have not yet been examined by lineament extraction. Therefore, this study aims to quantify the spatial density of lineament and examine a correlation between surface geothermal manifestations and lineament distribution by remote sensing techniques for the Nord-Ghoubbet geothermal area as a preliminary investigation. Lineament extraction was performed manually in this study. For manual lineament extractions, the shaded relief technique (the lineaments were extracted from 6 different azimuth angles (0° 45°, 90°, 180°, 200°and 315°), the filtering operation (based on a directional edge detection by different directions (NS, EW, NW, NE)), and image processing (False-color composite (FCC), a combination of band ratio methods, and principal component analysis (PCA)) were used to guarantee an impartial mapping of all lineaments in the study area. All manual lineament extractions were performed using QGIS. All lineaments obtained were overlain into a single shape file. After duplicate lineaments were removed, the final manual lineament map was created. This was accompanied by some lineament evaluation techniques such as lineament density and
orientation to extract additional lineament information. NW-SE trend, one of the main trends extracted here, is the general orientation of the faults in the study area. Conversely, N-S and WNW-ESE to E-W trends were less pronounced in the study area. The results of lineaments density were extracted manually. The analyses showed that the fumaroles are mainly located in high and medium density areas, suggesting that the structures may control the surface manifestation distribution.