Interpretasi Geologi Bawah Permukaan Berdasarkan Data Geomagnetik dan GPR di Area Hot Spring Natar - Cisarua, Lampung

Abstract

The geothermal manifestations in the form of hot springs at the Natar Hot Water Resource and the Cisarua hot spring bath are part of a geothermal system that has developed in the Lampung area. This study aims to interpret subsurface geological conditions and to identify structural controls governing the geothermal system within the study area using integrated geomagnetic and Ground Penetrating Radar (GPR) methods. Geomagnetic data processing involved diurnal correction and International Geomagnetic Reference Field (IGRF) correction applied to total magnetic field measurements to obtain Total Magnetic Anomaly (TMA) maps, followed by Reduction to the Pole (RTP) transformation to enhance anomaly positioning over their causative sources. In parallel, GPR data processing was conducted to generate high-resolution images of shallow subsurface structures. The results indicate that the hot spring manifestations are spatially associated with zones of low magnetic anomalies, interpreted as demagnetized rocks resulting from hydrothermal alteration processes. Furthermore, GPR profiles reveal chaotic and discontinuous reflection patterns, which are interpreted as altered zones acting as a cap rock (clay cap) within the geothermal system. The integration of geomagnetic and GPR datasets suggests that hydrothermal alteration and structurally controlled fluid pathways play a significant role in the development of geothermal manifestations in the study area