Identification Volcanostratigraphy with Fault and Fracture Density (FFD) Method for Geothermal Exploration; Case Study in Rajabasa Volcano, South Lampung District, Lampung

Nowadays, conventional energy production has decreased, so that the development of alternative energy is needed, one of which is geothermal energy. Geothermal potential can be produced by volcanic and non-volcanic processes. Until now, several geothermal areas that have been explored are the result of volcanic processes. One of them, the volcanic area that has geothermal energy potential is Rajabasa Volcano. Rajabasa Volcano in South Lampung District, Lampung Province. The method in this study is the study of literature using quantitative approaches, volcanostratigraphic analysis, and Fault and Fracture Desinty (FFD). Volcanostratigraphy analysis is done by identifying topographic maps, geological maps, geological data, and FFD methods using ArcMap, Global Mapper, and Surfer software. Studies on volcanostratigraphy and FFD can support geothermal exploration in a preliminary survey. Volcanostratigraphy and FFD identification aims to predict manifestations, volcanostratigraphic units, and geothermal prospect areas in the region. Based on volcanostratigraphy analysis, there is two crowns and one hummocky. The crowns consist of Rajabasa and Tangkil. The presence of the crown reflecting a long lived geothermal system. The results of FFD data processing show three zones, namely dark green-moss green (0-1.1 km/km²), light green-young orange (1.1-2.2 km/km²),  and orange-red (2.2-3.3 km /km²).  The red zone represents a high fracture density value in the region. This is evidenced by the discovery of manifestations of hot springs and fumaroles on the surface. Hot springs indicate the influence of geothermal and magma gradients that increase the temperature of the water from below the surface to the surface. Fumarole indicates the presence of magma at shallow depths, so that the water has boiled before reaching the surface. The existence of these two manifestations is based on FFD and the results of the correlation with volcanostratigraphy indicate that the research area has the potential to be carried out by geothermal exploration development.