## 2 The 1654 Earthquake: Geological, Seismological, and Macroseismic Context  
The earthquake hit during the early hours of the 24 th of July, producing destructive effects (I = 9-10, M = 6.3) [5] over a vast area of the Southern Latium region between Sora and Cassino and widespread damage on the southern side of the Fucino area (Figures 1 and 2). The map of the macroseismic intensities extends approximately 25 km from the epicenter, and the effects are differentiated, mainly because of different geological and topographical conditions of the villages involved. Six localities were almost completely destroyed and another twelve were heavily affected by the shock that was felt as far as Rome and Naples (IV-V MCS intensity). The relatively limited spatial distribution of the intensities associated with the 1654 earthquake partly reflects the paucity of official documents and historical sources available for this event. The economic marginality of the affected area (scarce productive activities, far from the main roads, no relevant  
Figure 1: Epicentral location of the 1654 earthquake (red star). The cities of Rome and Naples are less than 100 km of distance from the source. center damaged) did not encourage the authorities to send investigators (scientists and technicians) to produce detailed descriptions of the event, neither did the subsequent local historiography show interest in this seismic disaster. Additionally, the fact that this is a 'border' earthquake that occurred between the two former states of the Vatican and the Kingdom of Naples (Figure 2) may have played a role in the general knowledge of the event and further investigation could help to extend the map of damage. Despite this and except for the ancient 1349 M6.8 earthquake of which the location and magnitude are still debated [8,9], the 1654 Sora event is the most powerful earthquake to have occurred south of latitude 42\({}^{\circ}\) S and within 150 km southeast of Rome, representing the local seismic maximum for the study area (Figure 3). Figure 2: Map of the Mercalli–Cancani–Sieberg (MCS) intensities of the 1654 earthquake. A black star indicates the macroseismic epicenter of the event. The dashed line indicates the border between the two former states of the Vatican (West) and the Kingdom of Naples (East) in the XVII Century, at the time of the earthquake. Colored boxes are the modeled sources: BF, Balsorano fault; PF, Posta-Fibreno fault; SFa, Sora fault from ITHACA Working Group [12]; SFb, Sora fault from [PERSON] et al. [13]; MF, Macroseismic fault. Figure 4: \(\lambda\geq 2.5\) instrumental seismicity from 1985 (10) in the area of the 1654 earthquake (Latitude 41.45–41.90\({}^{\circ}\), Longitude 13.30–14.00\({}^{\circ}\)). In the inset, we show the parameters of the five M \(>4\) instrumental earthquakes that occurred in the area since 1984. A black star indicates the macroseismic epicenter of the 1654 event. Figure 3: Historical seismicity (5) of the southern Lazio region. The 1654 earthquake is the strongest event to have occurred in this area, apart from the 1349 event. The instrumental seismicity recorded in the area starting from 1985 [10] shows both low-to-moderate magnitude seismic sequences and diffuse swarm-like events, with the magnitude ranging from 0.4 to 4.8. Figure 4 reports the instrumental seismicity within 30 km from the 1654 epicenter, along with the focal mechanisms of the five most powerful (M \(\geq\) 4.1) seismic events in the study area that testify to a predominant normal faulting with an oblique left-lateral component [10, 11]. The 1654 earthquake area contains at least three main active tectonic lineaments [12], hereinafter referred to as the Balsorano fault (BF), Posta-Fibreno fault (PF), and Sora fault (SFa and SFb) (Figure 2 and Table 1), that are generally indicated as potential sources for this event because of their location and geometry. The three faults are closely spaced and they belong to the western system of active faults of the Central Apennines [13].