Harmonized inputs to PSHA: Seismic source zoning (SSZs) and earthquake catalogues across Northern Europe – Progress in 2024

Probabilistic Seismic Hazard Analysis (PSHA) is a broadly used methodology for estimating the probability of exceeding specific ground-motion thresholds within a given time frame. It is particularly crucial for nuclear power plants (NPPs), where safety assessments rely on accurate hazard quantification. PSHA integrates uncertainties related to seismic source characterization, historical and instrumental seismic data, ground-motion modeling, and uncertainty estimation. The NORDIC-SMART project focuses on improving seismic hazard assessments in Northern Europe by refining seismicity rate estimates and harmonizing hazard models. The project builds on previous Nordic research efforts and aims to develop a unified seismic source zoning (SSZ) model and a homogenized earthquake catalogue. These efforts address epistemic uncertainties, particularly in low-seismicity regions where small-magnitude earthquakes dominate historical records. A major challenge in the Nordic region is the lack of strong-motion recordings. To mitigate uncertainties, the NORDIC-SMART project aims to establish standardized procedures for estimating Gutenberg-Richter parameters. The first phase of the project focused on harmonizing SSZ models across national borders, integrating seismic data from multiple countries, and refining methodologies for earthquake catalogue compilation.