GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 Results of the correlaton analysis To assess the relatonship between the geological-geomorphological and hydrogeological study area features and ground deformaton in LAHC, a correlaton analysis has been carried out. We compared the vertcal deformaton, with slope maps, RS thickness, depth of regional aquifer and Vs of the outcropping lithologies. For each of these factors, the Pearson correlaton coefcient with ground vertcal average velocity has been calculated (Tab. 1). Table 1 – Values of the Pearson coefcients calculated between the considered geological predisposing factors and subsidence velocites. Furthermore, seasonal fuctuatons of subsidence velocity, as evidenced in Fig 1b, have been analysed. To this end, the cross-correlaton between quarterly average rainfall (mm/d) and detrended average subsidence rate (mm/y), has been analysed, in the tme range 2010-2021. A statstcally signifcant correlaton value, equal to 0.56, has been individuated. Discussion and perspectves for subsoil characterizaton by means of A-DInSAR displacement data The correlaton values in Tab. 1 are statstcally signifcant, nevertheless, it is presumable that the subsidence process is mainly controlled by the kind and thickness of lithologies involved. The above illustrated correlaton analysis provides a frst result, which may be improved by a multvariate approach, as described below. Fig.3 illustrates the velocity values associated with monitored points, falling in the strip (width: 50 m), indicated in semi-transparent red in Fig.3a, to achieve a more accurate comparison of ground displacement data with the subsurface structure. This band surrounds an accurate geological secton accomplished by Antonielli et al. (2020; Fig. 3b). Subsidence velocites decrease going from LAB 3 (with abundant fne and more deformable fracton) to LAB 2 and LAB 1 (Fig. 2), whereas, local variatons seem to be predominantly controlled by the RS thickness, as the trend of the point cloud in the diagram faithfully follows the thickness of the RS units (Figs. 3c and 3d). The results illustrated in Fig. 3d lead to conclude that a signifcant contributon to the observed subsidence phenomenon is provided by the consolidaton of Quaternary units. In In granular soils, seismic shaking produces well-known phenomena of variaton in porosity, such as compacton or dilatancy. In the case of saturated fne-grained soils (even above the water table) a frst phase of porosity variaton occurs slowly, associated with fuid expulsion (Terzaghi consolidaton), followed by a second phase of secondary consolidaton, due to creep phenomena. Predisposing factor Pearson coefficient Depth of regional aquifer -0.52 Ground slope -0.22 Red Soil thickness 0.13 Vs of outcropping geology 0.46