GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.1 GNGTS 2024 Corresponding author: laura.gulia@unibo.it Fault System Finite-Element Geodynamical Modelling for Seismic Hazard Analysis of the Central Italian Apennines A. Rood 1 , M. Pagani 1 , D. Di Bucci 2 1 GEM Foundation, Pavia, Italy 2 Dipartimento della Protezione Civile, Presidenza del Consiglio dei Ministri, Rome, Italy The structural complexity of the Italian Apennines, as a result of the sequential overprint of successive tectonic phases, presents a significant challenge in the study of the seismotectonics of the region for earthquake hazard analysis. Specifically, the effect of this structural complexity is that the interpretation of surface geological and geodetic observations may not completely characterise the 3-D distribution of fault geometries and their seismicity in the subsurface. Therefore, to understand the seismotectonics of the Apennines, for the goal of accurate seismic hazard analysis of this seismically active region, it is potentially valuable to characterise the seismogenic potential of faults both at surface and in the subsurface. The structural complexity of the Apennines and its consequences on the seismotectonic setting was recently emphasized by the pattern of seismicity across the Central Apennines during the 2016–2017 seismic sequence (Chiaraluce et al. , 2017). The reported fault segmentation, reactivation, and interaction within this fault system demonstrates the need for these phenomena to be taken into account when analysing the seismic hazard for this region (Buttinelli et al. , 2021a). To achieve this goal, we employed the RETRACE-3D model (Buttinelli et al. , 2021b) of the fault system that characterises the crustal volume affected by the 2016-2017 seismic sequence (Di Bucci et al. , 2021; RETRACE-3D Working Group, 2021) for use in geodynamic modelling using the Geodynamic World Builder (Fraters et al. , 2019). We then integrated this model with the finite element code ASPECT (Bangerth et al. , 2022; Kronbichler et al. , 2012) to determine the instantaneous long-term strain rate of each fault in the fault system. This is a new application of ASPECT to the modelling of active faults systems for seismic hazard analysis. Perhaps not unexpected, we find that major faults take over most of the extension imposed as a boundary condition (Stemberk et al. , 2019) and that the interaction between the faults within the fault system is evident from the spatial variability of strain rate over an individual fault surface.