## 1 Introduction
The strongest earthquake in the Italian study area occurred on 14 January 1703 (having M\({}_{\rm w}\) 6.9, and intensity XI MCS), and struck the Valnerina ([PERSON] et al., 2022 [19]; Table 1). All four strongest earthquakes for the CNAFS in the last 10 centuries occurred after 1700 A.D. (Table 1), and none of these four earthquakes are known as having fully ruptured the whole seismogenic fault system to which they are assigned in Table 1.  
The NMTFS generated several earthquakes of a magnitude larger than 8.0 in the last 10 centuries; therefore, these earthquakes have occurred repeatedly at intervals of 100 to 150 years along the Nankai Trough (e.g., [PERSON] et al., 2012 [20]; [PERSON] et al., 2022 [21]; Table 1). Through the definition of the moment magnitude ([PERSON] and [PERSON] 1979 [22]), we estimated the seismic moments released by the historical earthquakes reported in Table 1 since the year 1000 for the CNAFS and the NMTFS, obtaining \(5.23\,10^{19}\) Nm and \(4.60\,10^{22}\) Nm, respectively. In Italy, the causative sources of the main earthquakes of the study area are as follows: (1) the NW-SE-trending post-orogenic normal faults in the axial portion of the Apennines (e.g., [PERSON] et al., 2012 [23]), (2) the NE-verging syn-orogenic thrusts towards the Adriatic foreland (e.g., [PERSON] et al., 2015 [24]), and (3) the ENE-WSW-trending strike-slip faults bounding the Central Apennines thrust fronts to the South (DISS Working Group 2021 [25]). Most of the earthquakes of the CNAFS occurred between 1 and 15 km depth, above the basal detachment of the thrust fronts. The active extension is accommodated by normal faulting, which dominates along the hinge of the chain (e.g., [PERSON] et al., 2011 [26]). Figure 1: (**a**) A total of 43 seismogenic randomly colored fault systems—divided into 198 trapezoidal segments—straddling the northern and central Apennines (DISS Working Group 2021 [25]); (**b**) the Japanese megathrust fault system is divided into 5 fault segments ([PERSON] et al., 2012 [20]). Geometric and kinematics parameters of the seismogenic sources adopted in the simulator algorithm are shown in Tables S1 and S2 of the Supplementary Material. In Japan, the interface megathrust earthquakes occur between the overriding Eurasian/Amur continental plate and the subducting Philippine Sea oceanic plate. The seismogenic model of NMTFS is subdivided into five main 100-150 km long fault segments along the trough axis and almost corresponds to the distribution of forearc basins (e.g., [PERSON] et al., 2023 [27], and references therein). The seismogenic model of CNAFS includes 43 onshore and offshore seismogenic sources characterized by extensional and compressive kinematics (DISS Working Group 2021 [25]). Different fault mechanisms, fault sizes, and slip rates characterize the seismogenic sources of the two regions. Table 2 summarizes their main characteristics, while Tables S1 and S2 in the Supplementary Materials list the geometrical and kinematics parameters of the seismogenic sources adopted in the simulator algorithm of the CNAFS and the NMTFS, respectively (see [PERSON] et al., 2022b [15] and references therein). Notice that very different slip rates characterize the segments of the Japanese and Italian fault systems, and both systems can rupture separately or simultaneously with each other.