Identification of permeable zone in Kepahiang geothermal prospect area (Bengkulu) using integration of fault and fracture density method with gravity data

One of the remote sensing applications, namely the Fault and Fracture Density (FFD) method, was carried out to determine the permeable zone by assessing the lineaments' density level in Kepahiang geothermal prospect area Bengkulu Province. However, lineaments are not always due to fault activities only, so the digital image processing is carried out to enhance the fault and reduce other lineament effects. This research used Landsat 8 image processed through dimension reduction called Principal Component Analysis (PCA) and filtered using four different Convolution Filter such as Sobel, Line Detection, Prewitt, and Laplacian Filter. The lineaments then extracted automatically using the Edge Detection algorithm and compared with manually extracted lineaments from the IFSAR image to prove the effectiveness. In FFD maps, both Landsat 8 and IFSAR images showed the highest lineament density found in three zones: Mt. Kaba crater complex, Mt. Malintang, and at the Musi segment of the Sumatran fault system. Gravity data also used to validate the fault interpreted by First Horizontal and Second Vertical Derivative analysis. These results, integrated with other supporting data, showed the most permeable zone suitable for a well-target location near the Sempiang hot spring.