GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.3 GNGTS 2023 Matese massif deformations induced by hydrogeologic processes F. Pintori 1 , F. Sparacino 2 , F. Riguzzi 3 1 Istituto Nazionale di Geofisica e Vulcanologia sez. Bologna 2 Istituto Nazionale di Geofisica e Vulcanologia sez. Osservatorio Etneo, Catania 3 Istituto Nazionale di Geofisica e Vulcanologia sez. Osservatorio Nazionale Terremoti, Roma The Matese massif is an extensive outcrops of Apenninic Platform carbonate rocks located at the boundary between Central and Southern Apennines, extending ~74 km from NW to SE over an area of ~1600 km² and reaching a maximum height of 2050 m (M. Miletto). Its geological history documents different phases of compressional and extensional tectonics which modeled the shape and size of faults within the massif. The present seismotectonic background belongs to the extensional style of the central-southern Apennine chain, with a series of NW-SE active extensional faults and the occurrence of seismic activity, reaching in the past intensities up to IX MCS. Like other carbonate mounts, the Matese undergoes karst processes with significant response to hydrologic processes, linking rainfall trends to large variations of water reservoirs. Numerous recent papers highlighted the presence of deformations induced by the elastic response of the loaded surface and the poroelastic properties of the ground. These mechanisms are quite different, in the first case the water load causes subsidence, in the second uplift; both create horizontal deformations moving away from the centre of deformation. However, under anisotropic conditions, water pressure changes in poroelastic rocks can induce large horizontal deformations especially where highly fractured rocks may provide permeability for fluid flow. When the porosity is determined by systematic fractures, the medium is anisotropic and the surface deformation is mainly perpendicular to the fracture system. This is the condition of some carbonate massifs in the Apennines, like the Matese one, highly fractured by faults directed perpendicularly to the tectonic stress direction. Recent studies have shown that such deformations affect the GPS time series, if the stations are located on the fractured carbonates (e.g., D'Agostino et al., 2018; Devoti et al., 2018; Serpelloni et al., 2018; Silveri et al., 2019; Riguzzi et al., 2021; Pintori et al., 2021 and references therein). We have analyzed the time series of 7 GNSS permanent stations, located in the Matese area, and the seismicity, covering the 2005-2022 time interval. The GNSS time series of each station were detrended from a best-fitted linear model plus eventual steps due to instrumental changes, without modeling periodicities (annual, semi-annual). Therefore, we have obtained three time series of residual displacements (N, E, Up) for each site.