Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

Individual fault rupture probabilities The fault hazard analysis is applied on all 16 faults and Figure 4 shows the probabilities of the next rupture for ΔT= 50 years, for three models (Poisson, quasi-periodic BPT and cluster BPT models). As a general result: the largest probabilities for the Poisson model are obtained for faults with the shortest MIET. The highest probabilities for BPT period result for faults having the elapsed time approaching the MIET. The largest probabilities for the clustered BPT model are related to recently ruptured faults. Regional rupture probabilities In order to estimate the regional probability of future surface rupture earthquakes, given the uncertainties on data and temporal behavior of individual fault ruptures, we generate composite synthetic paleoseismic histories since 6000 BCE, by transferring the synthetic histories of ruptures on individual faults to a single timeline. In this way, we generate 10 6 regional synthetic histories without considering the possibility of inter-fault triggering of earthquakes. All of them indicate the Poisson model as a reliable distribution for the regional seismicity, given all sources of uncertainty involved in dating determinations. Since we do not have any evidence of a time- dependent, regional, earthquake occurrence, we adopt the Poisson model to compute the probability to have one surface faulting earthquake, at least, in the region, within ΔT years. The resulting probabilities of future surface faulting events in the studied portion of the Central Apennines are rather stable and close to 27% for the next 50 years. This probability do not take into account the contribution of possible unknown faults and, therefore, it may be a lower bound of the actual values. Fig.4: Values of probabilities for ΔT=50 yrs, calculated for each of the faults, for Poisson, quasi-periodic BPT and cluster BPT models (darker to lighter colored histogram columns, respectively) (Lombardi et al., submitted). Fault F4 has two different calculations considering two possible most recent events (the 1915 or 508CE as it ruptured in 1915 only sympathetically). The same is for Fault F10 but results are very similar. R E F E R E N C E S Bentley, J.L., T. Ottmann, (1979). Algorithms for reporting and counting geometric intersections. IEEE Trans. Comput. C-28 (9), 643–647. https://doi.org/10.1109/ TC.1979.1675432. Cinti, F.R., D. Pantosti, A.M. Lombardi, R. Civico, (2021). Modeling of earthquake chronology from paleoseismic data: Insights for regional earthquake recurrence and earthquake storms in the Central Apennines. Tectonophysics 816, 229016. Ellsworth, W.L., (1995). Characteristic earthquakes and long- term earthquake forecasts: implications of central California seismicity, in Cheng, F.Y., and Sheu, M.S., eds., Urban Disaster Mitigation: the Role of Science and Technology, Elsevier, p. 1-14. Lombardi, A.M., F.R. Cinti, D. Pantosti, (2024). Paleoearthquakes modeling and effects of uncertainties on probability assessment of next fault ruptures: the case of Central Italy surface faulting earthquakes, 2024, submitted. Rovida, A., M. Locati, R. Camassi, B. Lolli, P. Gasperini, (2020). The Italian earthquake catalogue CPTI15. Bull. Earthq. Eng. 18 (7), 2953–2984. https: //doi. org/10.1007/s10518-020-00818-y.