Integrating Ground Magnetic and Satellite Gravity Data for Delineating Geothermal System-Controlling Structures

Geothermal energy is a key renewable resource in Indonesia, including non-volcanic regions where subsurface conditions remain poorly understood. The Karangrejo–Tinatar area in Pacitan, East Java, displays hot spring manifestations that suggest a structurally controlled geothermal system. This study characterises the system using integrated primary ground magnetic data and GGMPlus satellite gravity data over a 25 km² area. Magnetic data were processed using Reduction to the Pole and Tilt Derivative, while gravity data were analysed through Bouguer correction, upward continuation, and 3D inversion modelling with ZondGM3D and Grablox 1.6. Results show magnetic susceptibility values ranging from −0.01759 to 0.0402 SI and rock density values from 1.88 to 3.11 g/cm³. The inversion model identified five major fault structures—Kebonsari, X, Karangrejo, Sedayu, and Tinatar Faults—that control geothermal fluid circulation as recharge and discharge pathways. This study provides a new framework for understanding non-volcanic geothermal systems in Indonesia.