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We model Coulomb stress transfer (CST) due to 30 strong earthquakes occurring on normal faults since 1509 CE in Calabria, Italy, including the influence of interseismic loading, and compare the results to existing studies of stress interaction from the Central and Southern Apennines, Italy. The three normal fault systems have different geometries and long‐term slip‐rates. We investigate the extent to which stress transfer can influence the occurrence of future earthquakes and what factors may govern the variability in earthquake recurrence in different fault systems. The Calabrian, Central Apennines, and Southern Apennines fault systems have 91%, 73%, and 70% of faults with mean positive cumulative CST in the time considered; this is due to fewer faults across strike, more across strike stress reductions, and greater along‐strike spacing in the three regions respectively. In regions with close along strike spacing or few faults across strike, such as Calabria and Southern Apennines, the stress loading history is mostly dominated by interseismic loading and most faults are positively stressed before an earthquake occur on them (96% of all faults that ruptured in Calabria; 94% of faults in Southern Apennines), and some of the strongest earthquakes occur on faults with the highest mean cumulative stress of all faults prior to the earthquake. In the Central Apennines, where across strike interactions are the predominant process, 79% of earthquakes occur on faults positively stressed. The results highlight that fault system geometry plays a central role in characterizing the stress evolution associated with earthquake recurrence. Plain Language Summary: Studies of fault interactions can improve our understanding of when and where the next earthquakes will occur. Here, we investigate how the orientation, length, location, and number of faults in a system influence the occurrence of future earthquakes, by modeling the stresses transferred during historical earthquakes and the regional stress in the Calabria region, southern Italy. We compare our results to similar models obtained for the Central Apennines and Southern Apennines in Italy. The Central Apennines hosts a complex fault system, with many overlapping faults, so that when an earthquake occurs, many of the surrounding faults experience a stress decrease. Whereas the Southern Apennines and Calabria have a simpler geometry, with fewer faults and less overlap, therefore the dominant process is stress increase. These characteristics influence the way faults build up stress, and we find that in regions with simpler geometry, a higher proportion of faults are positively stressed before an earthquake occurs on them, compared to regions with higher geometrical complexity. Our results show that fault system geometry plays a central role in characterizing the stress evolution associated with earthquake recurrence, and can possibly influence the occurrence of earthquake sequences that propagate between faults in a short time. Key Points: We compare Coulomb stress changes due to historical earthquakes and regional stress in three normal fault systems with different geometryFault system geometric complexity influences the number of faults that are positively stressed before they rupture in an earthquakeHigh slip rates and simple fault system geometry favor accumulation of high stress on faults and may promote triggered earthquake sequences [ABSTRACT FROM AUTHOR]

We investigate crustal deformation within the upper plate of the Ionian Subduction Zone (ISZ) at different time scales by (i) refining geodetic rates of crustal extension from continuous Global Navigation Satellite System (GNSS) measurements and (ii) mapping sequence of Late Quaternary raised marine terraces tectonically deformed by the West Crati normal fault, in northern Calabria. This region experienced damaging earthquakes in 1184 (M 6.75) and 1854 (M 6.3), possibly on the E-dipping West Crati fault (WCF) which, however, is not unanimously considered to be a seismogenic source. We report geodetic measurements of extension and strain rates across the strike of the E-dipping WCF and throughout the northern Calabria obtained by using velocities from 18 permanent GNSS stations with a series length longer than 4.5 years. These results suggest that crustal extension may be seismically accommodated in this region by a few normal faults. Furthermore, by applying a synchronous correlation approach, we refine the chronology of understudied tectonically deformed palaeoshorelines mapped on the footwall and along the strike of the WCF, facilitating calculation of the associated fault-controlled uplift rates. Raised Late Quaternary palaeoshorelines are preserved on the footwall of the WCF indicating that "regional" uplift, likely related to the deformation associated either with the subduction or mantle upwelling processes, is affected by local footwall uplift. We show that GIS-based elevations of Late Quaternary palaeoshorelines, as well as temporally constant uplift rates, vary along the strike of the WCF, implying normal faulting activity through time. This suggests that (i) the fault slip rate governing seismic hazard has also been constant over the Late Quaternary, over multiple earthquake cycles, and (ii) our geodetically derived fault throw rate for the WCF is likely a more than reasonable value to be used over longer time scales for an improved seismic hazard assessment. Overall, we emphasize the importance of mapping crustal deformation within the upper plate above subduction zones to avoid unreliable interpretations relating to the mechanism controlling regional uplift. [ABSTRACT FROM AUTHOR]