In 2016, a seismic sequence affected Central Italy, characterized by events with magnitudes exceeding Mw 5.0. This seismic activity is associated with the reactivation of the Vettore Mt.–Bove Mt. normal fault system, which comprises seismogenic structures capable of generating surface faulting. Among the seismic-induced effects, significant variations impacted the hydrogeological system of the Sibillini Mts., a hydrostructure of both local and regional importance. The most notable effects occurred following the October 30 seismic event, known as the Norcia earthquake (Mw 6.5). This event generated a considerable surface faulting along the western slope of the Vettore Mt. The hydrodynamic response of the hydrostructure was evident both at springs and along major watercourses, marked by anomalies in discharge rates. In particular, significant decreases in discharge were observed at high-altitude springs on the eastern slope of the Vettore Mt., whereas substantial increases occurred at springs located in the western sector. These variations were accompanied by changes and oscillations in piezometric levels, as well as alterations in water chemistry. The duration and magnitude of these changes, some of which are still evident, had significant consequences for the management of groundwater resources in the Sibillini Mts. area. Based on the conducted studies and current knowledge, the observed hydrogeological effects are attributed to changes in crustal permeability and variations in the pre-existing hydraulic gradient, caused by the rupture of the Vettore Mt. seismogenic fault, responsible for the October 30, 2016 event. This study aims to analyze the hydrogeological variations induced by the Norcia earthquake through the development of conceptual models and the application of numerical analyses. The objective is to investigate and understand the hydrodynamic behavior of the complex Sibillini Mts. hydrogeological system, and to test the hypotheses and mechanisms proposed to explain and justify the observed changes in hydrogeological regimes. Starting from the considerable amount of data and information available in the literature, a conceptual hydrogeological model of the examined hydrostructure was developed. The hydraulic and structural boundaries of the system were defined, refining a regional-scale model that includes all springs affected by discharge variations. This conceptualization integrates the several hydrogeological complexes recognized in the area into a single homogeneous aquifer, allowing for the delineation of a hydraulic functioning scheme. Active seismogenic faults are assumed to act as relative hydraulic barriers that compartmentalize the hydrostructure. The conceptual model was subsequently transferred and analyzed in a numerical framework. Groundwater flow scenarios, both pre- and post-earthquake, were simulated using two types of models. The first model (Semi-lumped Model) offers a simplified and straightforward configuration, designed to define the main hydraulic parameters of the investigated system and assess its response to variations in these parameters. A pre-seismic groundwater flow model was developed from it, and the obtained parameters were then calibrated and transferred to the second model. In the second model (Distributed Model), which is more spatially distributed and geometrically complex, the groundwater flow was simulated for both pre- and post-seismic scenarios. The post-seismic Abstract iii groundwater flow was simulated by modelling the hydraulic characteristics of the Vettore Mt. fault, whose rupture caused the instantaneous removal of the hydraulic barrier effect. The analyses performed and the models developed provide both qualitative and quantitative results that are consistent with the observed hydrogeological variations. These results confirm the initial conceptual assumption that faults can act as relative hydraulic barriers within the aquifer. The findings not only support existing theories but also provide a deeper insight into the hydrodynamics of the investigated system, facilitating a more comprehensive and detailed explanation of the significant discharge variations observed following the October 30 earthquake.
ANALYSIS OF HYDROGEOLOGICAL CHANGES INDUCED BY THE 2016 CENTRAL ITALY EARTHQUAKES: CONCEPTUAL AND NUMERICAL MODELS / Zullo, Enrica. - (2024 Dec 18).
ANALYSIS OF HYDROGEOLOGICAL CHANGES INDUCED BY THE 2016 CENTRAL ITALY EARTHQUAKES: CONCEPTUAL AND NUMERICAL MODELS
ZULLO, Enrica
2024-12-18
Abstract
In 2016, a seismic sequence affected Central Italy, characterized by events with magnitudes exceeding Mw 5.0. This seismic activity is associated with the reactivation of the Vettore Mt.–Bove Mt. normal fault system, which comprises seismogenic structures capable of generating surface faulting. Among the seismic-induced effects, significant variations impacted the hydrogeological system of the Sibillini Mts., a hydrostructure of both local and regional importance. The most notable effects occurred following the October 30 seismic event, known as the Norcia earthquake (Mw 6.5). This event generated a considerable surface faulting along the western slope of the Vettore Mt. The hydrodynamic response of the hydrostructure was evident both at springs and along major watercourses, marked by anomalies in discharge rates. In particular, significant decreases in discharge were observed at high-altitude springs on the eastern slope of the Vettore Mt., whereas substantial increases occurred at springs located in the western sector. These variations were accompanied by changes and oscillations in piezometric levels, as well as alterations in water chemistry. The duration and magnitude of these changes, some of which are still evident, had significant consequences for the management of groundwater resources in the Sibillini Mts. area. Based on the conducted studies and current knowledge, the observed hydrogeological effects are attributed to changes in crustal permeability and variations in the pre-existing hydraulic gradient, caused by the rupture of the Vettore Mt. seismogenic fault, responsible for the October 30, 2016 event. This study aims to analyze the hydrogeological variations induced by the Norcia earthquake through the development of conceptual models and the application of numerical analyses. The objective is to investigate and understand the hydrodynamic behavior of the complex Sibillini Mts. hydrogeological system, and to test the hypotheses and mechanisms proposed to explain and justify the observed changes in hydrogeological regimes. Starting from the considerable amount of data and information available in the literature, a conceptual hydrogeological model of the examined hydrostructure was developed. The hydraulic and structural boundaries of the system were defined, refining a regional-scale model that includes all springs affected by discharge variations. This conceptualization integrates the several hydrogeological complexes recognized in the area into a single homogeneous aquifer, allowing for the delineation of a hydraulic functioning scheme. Active seismogenic faults are assumed to act as relative hydraulic barriers that compartmentalize the hydrostructure. The conceptual model was subsequently transferred and analyzed in a numerical framework. Groundwater flow scenarios, both pre- and post-earthquake, were simulated using two types of models. The first model (Semi-lumped Model) offers a simplified and straightforward configuration, designed to define the main hydraulic parameters of the investigated system and assess its response to variations in these parameters. A pre-seismic groundwater flow model was developed from it, and the obtained parameters were then calibrated and transferred to the second model. In the second model (Distributed Model), which is more spatially distributed and geometrically complex, the groundwater flow was simulated for both pre- and post-seismic scenarios. The post-seismic Abstract iii groundwater flow was simulated by modelling the hydraulic characteristics of the Vettore Mt. fault, whose rupture caused the instantaneous removal of the hydraulic barrier effect. The analyses performed and the models developed provide both qualitative and quantitative results that are consistent with the observed hydrogeological variations. These results confirm the initial conceptual assumption that faults can act as relative hydraulic barriers within the aquifer. The findings not only support existing theories but also provide a deeper insight into the hydrodynamics of the investigated system, facilitating a more comprehensive and detailed explanation of the significant discharge variations observed following the October 30 earthquake.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.