## 3 Materials and Methods  
### Coulomb Failure Stress Changes  
The substantial energy released during earthquakes influences the stress conditions along fault surfaces, thereby facilitating or impeding subsequent fault movement to varying degrees [45]. Specifically, we use Coulomb failure stress (CFS) to investigate the stress relationships in the Earth's crust:  
\[CFS=|\tau|-[S-\mu(\sigma_{n}+P_{r})], \tag{1}\]  
where \(\tau\) is the shear on the fault plane, \(S\) is the cohesive stress in the fault medium, \(\mu\) is the internal friction coefficient, \(\sigma_{n}\) is the normal stress on the fault plane, and \(P_{r}\) is the pore pressure on the fault plane. As \(|\tau|\) moves closer to \(S-\mu(\sigma_{n}+P_{r})\), the rock breaks up more easily. The Coulomb failure criterion was derived by measuring the shear and normal stresses applied to rock samples in the laboratory [46]. However, in the Earth's crust, absolute stress values are difficult to measure. Although we may not know the absolute value of stress on a fault, we can calculate the Coulomb stress changes using the following expression by assuming that \(S\) and \(\mu\) do not vary with time [45; 46; 47]:  
\[\Delta CFS=\Delta\tau+\mu(\Delta\sigma_{n}+\Delta P_{r}), \tag{2}\]  
where \(\Delta\tau\) is the shear stress variation, and \(\Delta\sigma_{n}\) is the normal stress variation. After the change in static stress and the free-flowing fluid, the change in pore pressure is defined as  
\[\Delta P_{r}=-B\frac{\Delta\sigma_{ii}}{3}, \tag{3}\]  
where \(B\) is the Skempton coefficient, and \(\Delta\sigma_{ii}\) is the diagonal sum of the stress tensor, i.e., \(\Delta\sigma_{ii}=\Delta\sigma_{11}+\Delta\sigma_{22}+\Delta\sigma_{33}\). If \(\Delta\sigma_{11}=\Delta\sigma_{22}=\Delta\sigma_{33}\), then \(\frac{\Delta\sigma_{ii}}{3}=\Delta\sigma_{n}\), at which point ([PERSON] et al., 1994 [45])  
\[\Delta CFS=\Delta\tau+\mu\Delta\sigma_{n}, \tag{4}\]  
where \(\mu\) is the effective coefficient of friction, which takes values in the range 0-0.8.  
Figure 1: Schematic diagram of tectonic background and earthquakes. (**a**) Anatolian plate and neighboring plate tectonics illustration [43; 44]; (**b**) earthquakes occurred around the EAFZ (The white part of the focal mechanism represents tension and the black part represents compression). (source: [[https://deprem.afad.gov.tr/event-catalog](https://deprem.afad.gov.tr/event-catalog)]([https://deprem.afad.gov.tr/event-catalog](https://deprem.afad.gov.tr/event-catalog)) and [[https://www.isc.ac.uk/ischbulletin/search/mechanisms/](https://www.isc.ac.uk/ischbulletin/search/mechanisms/)]([https://www.isc.ac.uk/ischbulletin/search/mechanisms/](https://www.isc.ac.uk/ischbulletin/search/mechanisms/)), accessed date: 12 May 2024).  
When \(\Delta CFS>0\), it indicates that the fault is more prone to slip, and conversely, when \(\Delta CFS<0\), it indicates that the fault becomes more stable. Aftershocks are triggered when \(\Delta CFS>0.1\) bar ([PERSON] et al., 1995 [48]; [PERSON], 1998 [49]; [PERSON], 1999 [47]). In this study, we perform \(\Delta CFS\) calculations using Coulomb 3.4 software based on Okada in an elastic half-space with uniformly isotropic elastic properties [50; 51; 52].