Consistency between the Strain Rate Model and ESHM20 Earthquake Rate Forecast in Europe: insights for seismic hazard

Abstract. The primary aim of this research is to investigate how geodetic monitoring can offer valuable constraints to enhance the accuracy of the source model in probabilistic seismic hazard assessment. We leverage the release of geodetic strain rate maps for Europe, as derived by Piña-Valdès et al. (2022), and the ESHM20 source model by Danciu et al. (2024) to compare geodetic and seismic moment rates across Europe, a geographically extensive region characterized by heterogeneous seismic activity. Seismic moment computation relies on the magnitude-frequency distribution proposed in the ESHM20 source model logic tree, which is based on earthquake catalogs and fault datasets. This approach allows us to account for epistemic uncertainties proposed in ESHM20. On the geodesy side, we meticulously calculate the geodetic moment for each zone, considering associated epistemic uncertainties. Comparing the distributions of geodetic and seismic moments rates at different scales allows us to assess compatibility. The geodetic moment rate linearly depends of the seismogenic thickness, that is therefore a pivotal parameter contributing to the uncertainty. In high-activity zones, such as the Apennines, Greece, the Balkans, and the Betics, primary compatibility between seismic and geodetic moment rates is evident. However, local disparities underscore the importance of source zone scale; broader zones enhance the overlap between geodetic and seismic moment rate distributions. Discrepancies emerge in low-to-moderate activity zones, particularly in areas affected by Scandinavian Glacial Isostatic Adjustment, where geodetic moment rates exceed seismic moment rates significantly. Nevertheless, in some zones where ESHM20 recurrence models are well-constrained, by either enough seismic events in the catalogue or mapped active faults, we observe an overlap in the distributions of seismic and geodetic moments, suggesting the potential for integrating geodetic data even in regions with low deformation.