3D Fault Modelling of the Crati Basin (Northern Calabria, Southern Italy): Integrating Geology, Seismic Interpretation, Earthquake Analysis, and Geodetic Data for Hazard Assessment in an Active Tectonic Region

The Crati Basin, located in Northern Calabria (Southern Italy), is a tectonically active region with complex fault systems and notable seismic activity (Brozzetti et al., 2017a; 2017b; Cirillo et al., 2022; Lavecchia et al., 2024). Understanding the tectonic dynamics of this area is essential for evaluating the current seismic hazards. This study presents a comprehensive 3D fault modelling approach that integrates geological field observations, topographic analysis, interpretation of high resolution seismic reflection profiles, and geodetic measurements to map the fault system surface traces, define subsurface geometries and, ultimately, relate all the data to surface deformation. Integrating different datasets allowed building a detailed 3D structural model that provides insights into the spatial distribution and activity of fault systems in the basin. The findings highlight active fault segments, primarily exhibiting normal kinematics associated, in some cases, with a minor strike-slip component, consistent with the region's extensional tectonic regime. Moreover, the faults’s geometries are compatible with the recorded seismicity and related to geodetic data, emphasizing their role in earthquake generation and surface deformation. Seismic hazard assessment, based on the integrated model, identifies high-risk areas, particularly at fault intersections and zones of active strain, where seismic activity and surface deformation are more pronounced. In our study, we identify a 60-km-long, east-dipping master fault, as the primary structural feature controlling the Crati Basin, referred to as the Crati Graben Detachment Fault (CGDF). This fault represents the main expression of Quaternary extension in the area. It is characterized by a low-angle, east-dipping normal fault that outcrops along the eastern border of the Catena Costiera Calabra. The CGDF plays a pivotal role in shaping the basin, influencing its deep geometry and depositional evolution. It acts as a detachment horizon for both the synthetic high-angle normal faults (E-ENE dipping) and the antithetic high-angle normal faults (W-WSW dipping), which define the western and eastern boundaries of the basin, respectively. This comprehensive approach highlights the importance of integrating geological, geophysical, and geodetic data to construct reliable fault models for seismic hazard analysis in active tectonic regions. The results offer a basic framework for better understanding the active tectonics in Northern Calabria and provide valuable insights for regional planning and risk mitigation strategies.