3D upper crustal structure modelling in southwestern Sicily through multiapproach onshore–offshore data: insight into Sciacca Geothermal Field

This study investigates the architecture and structural setting of the Sciacca Fault System (SFS), a key component of the Sciacca Geothermal Field in southwestern Sicily, through an integrated geological and geophysical approach. The analysis correlates the offshore SFS lineament with the onshore Mt. Kronio fault system to assess their role in regional deformation and geothermal connectivity. Seismic reflection data reveal a NE–SW oriented transpressive fault network characterized by thrusts and positive structures, with evidence of recent compressive deformation affecting both Upper Calabrian deposits onshore and Late Pleistocene–Holocene sequences offshore. High-resolution profiles show active fluid migration, suggesting a hydraulically connected onshore–offshore geothermal system. A 3D reconstruction of the fault network defines the geometry and extent of the geothermal reservoir and supports a fluid migration model involving a northward and upward flow from a deep source in the offshore sector. Fluids are channelized within fault-bounded compartments sealed by low-permeability surfaces and capped by pelagic units, forming a partial structural trap. Vertical migration culminates where the carbonate substrate is exposed, as at Mt. Kronio, while offshore fluid ascent follows permeable faults and discontinuities within the sedimentary cover.