# The 2022 Seismic Sequence in the Northern Adriatic Sea and Its Long-Term Simulation
## 2 Seismotectonic Settings  
The northern Marche coastal belt and the Adriatic offshore area are characterised by a series of NW-SE trending, NE verging folds forming the easternmost edge of the Apennines thrust front (Figure 1; e.g., DISS_Working_Group [12], [PERSON] et al. [13], [PERSON] and [PERSON] [14], [PERSON] et al. [15]). This Apennines thrust front has progressively migrated toward the east-northeast all through the Tertiary-Quaternary (e.g., [PERSON] et al. [16]) and several geological evidence suggest that the folds are still growing and hence that the blind thrust fronts are active (e.g., [PERSON] et al. [13]). Especially in the offshore area the interpretation of seismic reflection profiles is strategic to understanding the geometry of the active faults (e.g., [PERSON] et al. [17]). The occurrence of historical and instrumental earthquakes (e.g., 1672, 1690, 1786, 1875, 1916, 1924, 1930, all with \(Mw\geq 5.5\); Table 1; Figure 1) suggests that the thrust faults are also seismogenic. The earthquakes in the area have often generated a tsunami; subsequently, their causative faults have been able to produce significant vertical displacement of the ground surface or sea floor, and are very close to the coast or offshore (Table 1; [PERSON] et al. [19]). A relevant aspect of seismic activity in the study area, as in the rest of Italy (e.g., [PERSON] et al. [20]), is the occurrence of seismic sequences with more than one main shock of similar magnitude (Table 1). These sequences can be distinguished from typical aftershock sequences because the difference between the largest and second-largest magnitudes is relatively small and does not follow the so-called \"Bath Law\" (see [PERSON] et al. [7]). Figure 1: Seismotectonic framework of the northern Marche coastal and offshore area. The seismic sequence from 9 November to 14 February 2023 is shown in light blue ([[http://terremoti.ingv.it/](http://terremoti.ingv.it/)]([http://terremoti.ingv.it/](http://terremoti.ingv.it/)), accessed on 14 February 2023); historical and instrumental earthquakes from CPTII5 are shown with coloured squares ([PERSON] et al. [18]), earthquakes with \(M_{w}\geq 5.5\) are labelled (see Table 1); surface projection of Composite Seismogenic Sources from DIS 3.3.0 are shown with orange ribbons ([[https://diss.ingv.it](https://diss.ingv.it)]([https://diss.ingv.it](https://diss.ingv.it)), accessed on 14 February 2023; DISS_Working_Group [12]). Focal mechanisms of the 9 November 2022 earthquake and the 30 October 1930 event are from TDMT ([[http://webservices.ingv.it/webservices/ingv_ws_map/data/tdmt/19591/111604601_15](http://webservices.ingv.it/webservices/ingv_ws_map/data/tdmt/19591/111604601_15)]([http://webservices.ingv.it/webservices/ingv_ws_map/data/tdmt/19591/111604601_15](http://webservices.ingv.it/webservices/ingv_ws_map/data/tdmt/19591/111604601_15)) 4_tdmt_reviewer_solution.pdf, accessed on 14 February 2023), and [PERSON] et al. [19]), respectively. A seismic sequence with two events of similar magnitude also began on 9 November 2022. As a matter of fact, at 06:07:25 UTC a \(M_{w}\)5.5 earthquake struck the northern Marche offshore area, and only one minute later, a \(M_{l}\)5.2 earthquake struck about 7 km to the south ([[http://terremoti.ingv.it](http://terremoti.ingv.it)]([http://terremoti.ingv.it](http://terremoti.ingv.it)), accessed on 14 February 2023; Figure 1; Table 1). According to the hypocentral location of these two mainshocks, the ITCS106 fault system is retained the causative source of the sequence. More than 900 aftershocks occurred offshore Pesaro and Senigallia from 9 November 2022 to 14 February 2023 (Figure 1). The occurrence of this sequence demonstrates that the buried offshore thrust front, included in the Database of Individual Seismogenic Sources since 2013 despite the absence of historical and recent seismicity (DISS_Working_Group[12]), is active and seismogenic.