Conditional probability of surface rupture: A numerical approach for principal faulting

This study presents a numerical approach for probabilistic fault displacement hazard analysis (PFDHA), aimed at addressing an alternative solution to commonly used empirical methodologies. Our model utilizes probability distributions to compute the conditional probability of surface rupture (CPSR). Leveraging earthquake catalogs, we derived the hypocentral depth distribution (HDD) across eight globally distributed seismotectonic regions categorized by faulting kinematics (normal, reverse, strike-slip). We calculated the hypocentral depth ratio (HDR) distribution, to model rupture position from the hypocenter. Rupture widths are estimated as a function of magnitude based on previously published scaling relations. User-input parameters, including fault style, average dip angle, and seismogenic depth, with associated uncertainties, derive the CPSR estimation of surface rupture occurrences. Our findings highlight seismogenic depth as the most influential parameter and reveal correspondences between empirical curves derived for specific regions. These findings support the use of source-specific surface rupture probability assessments over approaches based on global datasets, and underscore the importance of considering the local seismotectonic setting when evaluating fault displacement hazard. The numerical code for CPSR calculation has been developed and is openly accessible on GitHub.