# The 2022 Seismic Sequence in the Northern Adriatic Sea and Its Long-Term Simulation
## 3 Earthquake Simulation Method  
Our simulator code's algorithm was originally introduced by [PERSON] et al. [8], and subsequently modified in different versions with the inclusion of new features, as described by [PERSON] et al. [7; 9]. The present study employs the following fundamental principles of the simulator algorithm:  
1. The simulation of seismic sources involves the use of planar quadrilateral fault segments with specific spatial position, shape, and size. To accurately represent the various seismic events that may occur, each fault segment is discretized by square cells with sizes determined by the minimum magnitude of events expected in the output simulated catalogue. 2. At the start of the simulation, stress values are randomly assigned to each cell from a specified stress range. This randomization is essential to ensure that the simulation represents the natural variation in stress levels that exists in real-life seismic events. 3. Every fault segment is subjected to constant and uniform tectonic stress loading. This loading is based on geologically or geodetically inferred slip rate, providing the simulation with a more accurate representation of the tectonic stresses that occur in real seismic events. \begin{table}
\begin{tabular}{c c c c c} \hline
**ID** & **Date** & \(\mathbf{M_{w}}\) & \(\mathbf{I_{o}}\) & **Multiple** & **Associated Tsunami with Intensity** \\ \hline
1 & September 1269 * & 5.6 & VIII & n.a. & Generated by a landslide ** \\
2 & 14 April 1672 & 5.6 & VIII & n.a. & SA:3; PI:IV \\
3 & 23 December 1690 & 5.6 & VIII & n.a. & SA:3; PI:IV \\
4 & 25 December 1786 & 5.7 & VIII & T *** & No record \\
5 & 17 March 1875 & 5.7 & VIII & n.a. & SA:3; PI:IV \\
6 & 17 May 1916 & 5.8 & VIII & T & No record \\
7 & 16 August 1916 & 5.5 & VI & T & SA:2; PI:IV \\
8 & 2 January 1924 & 5.5 & VII-VIII & n.a. & No record \\
9 & 30 October 2022 & 5.5 & V *** & T & No record \\ \hline \end{tabular}
\end{table} 
Table 1: Historical and instrumental earthquakes with \(M_{w}\geq 5.5\) of the study area (Figure 1; CPT15; [PERSON] et al. [18]; CFT15 Med; [PERSON] et al. [21]), and tsunami with their intensity (EMTC; [PERSON] et al.[22]). T: true; SA: Intensity Sieberg–Ambraseys scale; PI: Intensity Papadopoulos and Imamura scale; * unspecified day; ** the earthquake triggered a large landslide that fell into the sea on the eastern side of Monte Conero (CFT15 Med[21]); *** some historical sources describe the occurrence of a second large earthquake one hour after the first event (CFT15 Med[21]); *** EMS-98 scale; [PERSON] et al.[2]. 4. The simulation involves the nucleation of a new event in a cell when its stress exceeds a given threshold strength. This threshold strength is essential to accurately model the conditions that trigger seismic events in reality. 5. Whenever a cell ruptures, a co-seismic stress-drop of 3.3 MPa is assigned to it. This stress-drop is a crucial aspect of the simulation as it represents the stress released by the rupturing cell, which is a significant factor in the generation of seismic events. 6. Following the rupture of a cell, the co-seismic Coulomb stress is transferred from the rupturing cell to all other neighbouring cells. This transfer occurs based on the theory of elasticity, taking into account the strike, dip, and rake of each cell. 7. The rupture expands to neighbouring cells based on heuristic rules that simulate a weakening mechanism. These rules are based on the behaviour of real-life seismic events and are essential to accurately represent the spread of a seismic event. 8. If the positive Coulomb stress transferred from neighbouring cells causes a cell's status to exceed the threshold strength, it is allowed to rupture more than once in the same earthquake. This is an important aspect of the simulation as it allows for the accurate representation of aftershocks and the complex nature of seismic events. 9.