Consistency of seismic hazard estimates from a physics-based earthquake simulator: a case study in south-eastern Spain

Estimating seismic hazard is crucial for enhancing societal resilience and risk mitigation strategies. Probabilistic Seismic Hazard Analysis (PSHA) is the current standard framework, traditionally relying on empirical earthquake rupture forecasts (ERFs) and ground-motion models. In this framework, physics-based earthquake cycle simulators are emerging as powerful tools in PSHA, capable of replicating observed seismicity and seismic hazard statistics. Here, we present a quantitative consistency evaluation of physics-based PSHA models at the Eastern Betic Shear Zone in south-eastern Spain against both historical macroseismic intensity data and instrumental ground shaking records. We use synthetic catalogues from RSQSim earthquake-cycle simulations to construct two physics-based ERFs that we pipeline into a PSHA calculation. Results indicate that the physics-based ERFs derived from the best-performing simulation model, previously ranked against empirical benchmarks, achieve the best overall agreement with observed macroseismic intensities and acceleration records at 10 sites, outperforming both the lower-performing simulation and a traditional area-source model. Our findings highlight that the incorporation of physics-based models into PSHA is appropriate, inherently enabling the inclusion of fault-system rupture complexity and interactions, all key challenges in PSHA. We also advocate for the hybridization of physics-based models with traditional approaches in PSHA to better capture epistemic uncertainties in the hazard representation.