GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 Fig. 1 - 3D simplified geometric model representing the main regional structures and the reconstructed bottom surface of the Basal aquifer of the Sibillini Mts. SMT: Sibillini Mts. Thrust; VBFS: Vettore-Bove Fault System; FVT: Fiegni-Vettore Thrust; NFS: Norcia Fault System. Then a numerical analysis was performed by using the USGS MODFLOW 6 code to create a regional scale hydrogeological model in steady-state conditions, to simulate the groundwater flow before the earthquake. We defined a modelled area of about 1020 km 2 , according to tectonic and hydrogeological features. To evaluate the groundwater filtration along fault zones and the effect of faults as hydraulic barrier during the pre-rupture condition, we implemented both the Vettore-Bove and Norcia faults in our hydrological model by assigning them a lower permeability value. The result is a distribution of the hydraulic head very close to faults (Fig. 2), reflecting a high loss of hydraulic gradient and a prevailing north-westward direction of groundwater flux. This qualitative result is consistent with the pre-seismic measured discharge values and water-levels observations.