GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.3 GNGTS 2023 We have also analyzed spring discharge and pluviometric data available in the study region. As regards pluviometric data we focus on the rainfall excess, which has been computed as the difference between the cumulated daily rainfall and the best-fitting straight line of the cumulated rainfall. Then we have applied an Independent Component Analysis (ICA, Gualandi et al., 2016) to the GNSS data. This has allowed us to extract from the time series, in a blind way, a signal (IC2) that is very well correlated with the hydrological data (Fig. 1). This geodetic signal has a large horizontal amplitude and occurs perpendicular to the fracture orientations. During wet periods, which are characterized by excess of rainfall and increasing values of spring discharge, we observe an extensional deformation, with stations moving “away” from the center of the Matese massif; while during dry periods a compressional deformation occurs, so that the GNSS stations move “toward” the massif. This suggests that the driver of this geodetic signal is the water stored within the massif: the more it increases the larger the water pressure, which causes extensional deformation; while when the water level decreases the water pressure is reduced and then compressional deformation occurs. The horizontal strain tensor estimated from the IC2 maximum displacements shows clearly what is stated above: during the oscillation, the axis of maximum extension can reach up 1µstrain and its direction is perpendicular to the fault direction (Fig. 2). Further work should be done to understand if water circulation also indirectly affects the background seismicity.