GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 creates a new flow section to favor a groundwater transfer through the fault. This involves a variation of the hydraulic gradient and of groundwater divide in hydrogeological systems. The 2016 Central Italy seismic sequence, which resulted from the rupture of different segments of the Vettore-Bove normal fault system, caused an important hydrogeological imbalance of the carbonate aquifers of the Sibillini Mts. Sustained variation in groundwater flow occurred especially after the M w 6.5, 30 October main shock which struck Norcia town, the most important of which include: i) a general increase in discharge at the springs bordering the western side of the Sibillini Mts. and along the main drainage system of the Nera River basin; ii) the reappearance of Torbidone spring in the Norcia plain, dry since 1979 (Valigi et al ., 2019; Petitta et al ., 2018); iii) a strong discharge reduction and water-table decrease at the springs located on the eastern side of the Sibillini Mts., such as to cause several problems with regard to the water supply system for the Marche region. According to Mastrorillo et al . (2020), the “aquifer fault rupture” mechanism better explain the observed permanent variations, suggesting an eastward shift of the piezometric divide of Vettore Mt. The purpose of this work is to assess the hydrodynamic response of the fractured carbonate aquifer system of the Sibillini Mts. to the coseismic dislocation of Vettore fault, through the realization of 2D and 3D numerical models. We collected geological and hydrogeological data from the available literature to create a geomechanical model of the seismogenic fault rupture and a hydrogeological model to simulate the groundwater flow before and after the 30 October earthquake. Preliminary results We first defined a hydrogeological conceptual model, which represents the supporting structure of numerical analysis. We created a simplified 3D geometric model at surface scale (up to 2 km depth) to define the spatial relations between the main tectonic structures and the boundaries of the hydrogeological complexes (Fig.1).