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

I N T R O D U C T I O N Earthquake surface faulting can be the source of hazard for critical infrastructure located close to the trace of a capable fault. Zonation and avoidance strategies are common practices during the design of new infrastructure, but this option can be not feasible for existing facilities. This issue can be addressed by Probabilistic Fault Displacement Hazard Analysis (PFDHA). PFDHA assesses the likelihood of exceeding a certain level of displacement at the site of the infrastructure. The resulting hazard curves can help to choose the most appropriate mitigation strategies. Since the beginning of the current century, empirical regressions have been proposed to assess the probability of surface displacement at a site of interest, for both Principal (or primary) and Distributed (or secondary) faulting. While PFDHA methods for Principal faulting have been largely improved in the last years (e.g. , Sarmiento et al . , 2023, including aggregated principal and distributed displacement), much less effort has been dedicated to Distributed rupturing (DR). So, PFDHA of DR is a major challenge in PFDHA. The existing methods and regressions for PFDHA of DR suffer of some major issues, such as paucity of empirical data populating current regressions, particularly for extensional setting, and impossibility of distinguishing between reactivation of known pre- existing faults/discontinuities and ‘random’ ruptures on new (or previously unknown) secondary structures. Then, we propose novel regressions based on a denser set of DR data extracted from the SURE 2.0 database (Nurminen et al., 2022) for dip-slip (normal and reverse) faults. We also propose an original approach for combining different DR regressions in PFDHA, based on geologic knowledge of the site under investigation.