Advancing Probabilistic Seismic Hazard Assessment for Northeastern Brazil: Toward a Comprehensive Treatment of Epistemic Uncertainties

This study presents an updated probabilistic seismic hazard analysis model for Northeastern Brazil, a stable continental region, taking into account more comprehensive epistemic uncertainties compared to previous studies, which is critical for robust decision making related to earthquake risk management. The model incorporates updated models and datasets, and provides gridded values of seismic hazard for various intensity measures, return periods, and site conditions across the study region. In addition, more detailed results are provided for selected locations to support engineering applications. Sensitivity analysis is also carried out to identify possible relevant parameters that deserve further investigations. The results reveal that peak ground acceleration across the target region remains below 0.05 and 0.22 g for return periods of 475 and 2475 years, respectively, and an average shear wave velocity of 760 m/s, supporting the current classification of the region as Zone 1 of the seismic design code (PGA 0.05 g for the 475‐year return period). Variations in hazard levels across the study area, relative to previous models and design ground motions, have potential implications for risk assessments and suggest the need to revisit seismic design zones and spectrum shape. Sensitivity analysis indicates that the minimum magnitude considered in hazard calculations and the incorporation of regional characteristics into ground motion models have the potential to significantly affect hazard estimates, highlighting the need for further investigations in the future.