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 past 100 years have seen the occurrence of five Mw> 9 earthquakes and 94 Mw> 8 earthquakes. Here we assess the potential for future great earthquakes using inferences of interseismic subduction zone coupling from a global block model incorporating both tectonic plate motions and earthquake cycle effects. Interseismic earthquake cycle effects are represented using a first-order quasistatic elastic approximation and include ~10^7 km^2 of interacting fault system area across the globe. We use estimated spatial variations in decadal-duration coupling at 15 subduction zones and the Himalayan range front to estimate the locations and magnitudes of potential seismic events using empirical scaling relationships relating rupture area to moment magnitude. As threshold coupling values increase, estimates of potential earthquake magnitudes decrease, but the total number of large earthquakes varies non-monotonically. These rupture scenarios include as many as 14 recent or potential Mw>9 earthquakes globally and up to 18 distinct Mw> 7 events associated with a single subduction zone (South America). We also combine estimated slip deficit rates and potential event magnitudes to calculate recurrence intervals for large earthquake scenarios, finding that almost all potential earthquakes have a recurrence time of less than 1,000 years.