GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 we were able to construct 3D fault models, drawing from actual traces and determining a slip distributon for each fault. We chose to compute the Coulomb stress for each fault segment, maintaining a consistent fricton coefcient. Where available, we used actual slip data for recent earthquakes. For less documented seismic events, we assumed a centered slip distributon, reminiscent of a bull's eye patern, depending on the relatve seismic moment. In instances where the fault width wasn't specifed in the reviewed literature, we used standard geometric relatonships (Gupta and Scholz, 2000) to determine it, basing our calculatons on a 1.5 aspect rato (length/width). For faults with an extended length, their maximum depth was aligned with the thickness of the seismogenic layer, approximately 15 km (Gasparini et al., 1985; Chiarabba and De Gori, 2016). To optmize CST data comprehension, we crafed three distnct representatons. Initally, a traditonal CST map was produced at a depth of 5 km, in plan view, providing an approximaton of CST distributon within the surrounding crust. This informaton was then translated to KML format for georeferenced visualizaton on Google Earth Pro. Lastly, we crafed cross-sectons perpendicular to fault strikes and developed a 3D model of the fault planes, obtaining the CST values for each 1 km fault segment, thus ensuring heightened precision in the assessment of stress for each individual segment. In many of the case studies, CST may have played an infuental role within the CAFS (Fig. 1 and Fig.2), catalyzing the actvaton or inhibiton of its faults. Several instances highlight fault reactvaton following high stress transfer in short periods, some examples are described below: ● The 1279 Colforito earthquake positvely stressed the northern tp of the Norcia fault, that ruptured in 1328. ● The 1703 Norcia earthquake positvely stressed the Pizzoli fault, where few days later a huge earthquake nucleated, provoking a cascade efect engaging the Petno and Paganica faults. ● The 24 th august and 26 th October 2016 earthquakes seems to have stressed the bends and the central porton of the Vetore fault, probably facilitatng the 30 th October complete rupture. ● The Colforito fault system stored conspicuous amount of positve stress from each of the earthquakes generated by the Norcia fault system probably infuencing its reactvaton in 1997. ● The 1703 Norcia earthquake generated a huge positve stress lobe towards the Fabriano area, where 38 years later a destructve earthquake struck. Conversely, certain scenarios illuminate the calming efect of stress shadows. Some examples include: ● The Vetore fault generated only one earthquake during the last millennium, this could be linked to the parallel Norcia fault that ruptured 4 tmes in the same tme span, transferring negatve CST on the Vetore fault.