Extensional faults in Southern Calabria (Italy) have been widely studied for their capability to generate high magnitude earthquakes (Mw 7-7.2). An example is the 1783 historical seismic sequence, which caused numerous fatalities near the villages located along the largest fault structures of this region, the Cittanova fault and the Serre fault. In this paper, we estimated the seismic potential of these two faults by a kinematic block modeling approach using GNSS data of both campaign points and permanent stations available within this area. Our results indicate that both faults are accommodating extensional velocity gradient (~ 1 mm/yr), with long-term slip rates (~ 2 mm/yr). A 3D mesh of triangular dislocation elements (TDEs) was used to estimate the spatial variability of the back-slip on fault planes, the corresponding interseismic coupling degree and the resolution capability related to the data spreading. This approach has allowed us to distinguish the fault areas where elastic seismic rupture is more likely to happen from those affected by aseismic creeping behaviour. Using our interseismic coupling results, we estimated a set of possible rupture scenarios in Southern Calabria, as well as calculated the corresponding interseismic moment accumulation rate, comparing it to the coseismic moment release rate achieved by previous studies. Thus, we achieved that, the Southern Calabria domain is accumulating an interseimic moment rate at most equal to 1.09 ×1015 Nm/yr, the equivalent of an earthquake of Mw 4 for each year.

The 2016-2017 Central Italy earthquake sequence struck the central Apennines between August 2016 and October 2016 with Mw ∈ [5.9; 6.5], plus four earthquakes occurring in January 2017 with Mw ∈ [5.0; 5.5]. Here we study Global Positioning System (GPS) stations active during the post-seismic phase including near and far-field domains. We separate the post-seismic deformation from other, mainly seasonal, hydrological deformation signals present in ground displacement time-series via a variational Bayesian Independent Component Analysis technique. For each component, realistic uncertainties are provided to the related ICA-reconstructed displacement field. We study the distribution of afterslip on the main structures surrounding the mainshock, and we highlight the role played by structures that were not activated during the co-seismic phase in accommodating the post-seismic deformation. In particular, we report aseismic deformation occurring on the Paganica fault, which hosted the Mw 6.1 2009 L’Aquila earthquake, and is located further south of the 2016-2017 epicenters; and on a 〜2-3 km thick subhorizontal shear-zone, clearly illuminated by seismicity, which bounds at depth the west-dipping normal faults where the mainshocks nucleated. Since afterslip alone underestimates the displacement in the far-field domain, we consider the possibility that the shear zone marks the brittle-ductile transition, assuming the viscoelastic relaxation of the lower crust as a mechanism contributing to the post-seismic displacement. Our results suggest that multiple deformation processes are active in the first two years after the mainshocks.