GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 faults could potentally bridge it, in light of the Coulomb Stress Transfer analysis and the distributon of seismicity over the last millennium. In recent tmes, there has been a renewed focus on investgatng the tectonic and seismic features of the CAFS. This intensifed commitment has fostered a deeper understanding of fault dynamics, stress interactons between them, and forecasts for future seismic actvites. Given the intricate tectonic nature of the CAFS and its pronounced seismicity, the imperatve for consistent research and monitoring in this domain becomes clear. A cornerstone in seismic risk assessment is grasping the Coulomb stress transfer mechanism among faults. This study delves into this partcular facet within the CAFS, accountng for the most signifcant seismic events over the last 750 years. Both historic earthquakes and recent seismic occurrences are analyzed to determine potental future seismic scenarios. By evaluatng both the magnitude and the proximity to other fault lines that ruptured shortly afer the primary event, we have chosen to concentrate on 9 of these earthquakes in relaton to the Coulomb stress transfer (CST). The comprehensive list of these earthquakes, along with their specifc atributes, is presented in Table 1, highlightng the ones selected for the CST analysis. The seismic occurrence of 1349 AD was re-evaluated and updated based on the recent fndings by Galli et al. (2022). Within the framework of our research, we've operated under the assumpton that subsequent to seismic actvity on a specifc fault, Coulomb stress can propagate to neighboring faults. If this stress is positve, it might encourage fault rupture, whereas if negatve, it could deter it (King et al., 1994). Numerous factors, including the distance between the causatve fault and its neighboring one, their shapes, positons, dynamics, and the slip of the source fault, infuence the Coulomb stress changes. Utlizing the "Coulomb 3.4" sofware, we derived the CST using the equaton (Lin and Stein, 2004; Toda et al., 2005): ΔCST =Δτs+μΔσn In this equaton, ΔCST represents variatons in Coulomb Stress Transfer, Δ s corresponds to shifs in shear stress, while stands for the fricton coefcient, and Δ n signifes alteratons in normal stress. We adopted a fricton coefcient of 0.6 (Galderisi and Galli, 2020) and opted for default spatal parameters with a Poisson's rato of 0.25 and a Young's modulus of 800,000 bar. Regarding the three-dimensional portrayal of faults within CST calculatons, we leaned on the methodology proposed by Valentni et al., (2023). We integrated a three-dimensional model featuring strike variatons and an elliptcal shape into our CST algorithm, believing that an accurate representaton of the CAFS is pivotal to reducing potental computatonal inaccuracies. In advancing with the CST simulatons, we endeavored to mirror the real seismic rupture dynamics, factoring in variables such as the slip distributon or the partal or entre rupture. To ensure sharp graphical detail and enhanced bar value precision, we established a 1 km grid for the fault modeling. Faults, perceived in an elastc half-space, were outlined as lines with variable strike and segmented into 1 km units. This intricate segmentaton proved to be a balanced choice between output detail and modeling duraton, deviatng from the more typical practce of using 2 km segments for CST modeling. Subsequently, using the "Faults 3D" sofware (Mildon et al. 2016),