How earthquakes reshape carbonate aquifers: Modelling groundwater redistribution in Central Italy after the October 2016, Mw 6.5 Norcia earthquake

Study region: The carbonate hydrostructures of the Italian Apennines host major aquifers that serve as a critical groundwater resource. In tectonically active settings, such as the Sibillini Mountains, structural discontinuities and deformation features exert a dominant control on the hydraulic conductivity and storage properties of aquifers, thereby modulating groundwater flow regimes. Study focus: The Mw 6.5 Norcia earthquake of October 30th 2016, part of the 2016 Central Italy seismic sequence, caused extensive ground deformation and surface faulting, triggering signifi cant and long-lasting hydrogeological changes across the Sibillini Mountains carbonate aquifer. In this study, we develop a regional-scale conceptual hydrogeological model and implement it in steady-state numerical simulations. Our modelling reproduces pre- and post-seismic groundwater flow conditions and highlights the role of major active faults in governing aquifer hydrodynamics. New hydrological insights for the region: Simulations demonstrate that the earthquake-induced fault rupture, modelled as a binary (on-off) feature, facilitated cross-fault groundwater transfer, leading to a persistent depletion of the eastern aquifer sector and enhanced discharge in the central and western sectors. These findings provide evidence of how seismic events can reconfigure groundwater flow patterns in fractured carbonate systems, highlighting the critical role of tectonic structures in controlling their hydrodynamic balance.