GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.2 - POSTER GNGTS 2023 The results for the linear elastic model (Figure 2a) show typical inflationary displacement patterns characterised by maximum ground uplift at the symmetry axis of the model, while horizontal displacements are null at the symmetry axis, then gradually increase moving away until reaching the maximum value at approximately 3 km distance (Figure 2b). The vertical displacements time-series increase linearly over the modelled timespan, according to the linear increase of overpressure in the volcanic magma chamber (Figure 2d). The results of the poroelastic model with linear inflation show that, at the end of the inflation process, an excess pore pressure pattern has developed nearby the simulated inflation source (Figure 2c). Outside the source, the stress field shows the typical pattern of the crack opening, with dilatation at the top and bottom of the source and at the source tips. This excess pore pressure distribution triggers a progressive fluid flow diffusion from areas characterised by overpressure to areas affected by underpressure. A sustained groundwater flux develops from the top of the inflation source to the ground surface. This fluid flow, which is continuous over the investigated timespan, fuels the shallower hydrothermal field, supporting the evidence of changes at the Solfatara area. The vertical displacements increase linearly, but at a lower rate than the linear elastic model (Figure 2d). This is probably due to the stress partitioning between the mechanical component and the fluid one. Finally, the third poroelastic model assumes an impulsive source inflation, and the highest pore pressure excess develops immediately after the application of the impulsive load (Figure 2e). Subsequently, pore pressure excess gradually dissipates because of the triggering of fluid diffusion from the source to the ground surface (Figure 2f). Consequently, fluid diffusion produces further uplift at the symmetry axis of the model (Figure 2d), thus confirming that poroelastic-related ground deformations agree with those caused by the source inflation only. Results confirm that fluid flow induced by the poroelastic deformation of the magma chamber is a plausible mechanism to explain the fueling of the hydrothermal system. Moreover, poroelastic induced ground displacements are not negligible and should be adequately considered. From these preliminary results, 3D models will be developed in the future, accounting for the elastic heterogeneities of the local crust.