HybridModel: an improved tool for distributing fault-type and zone-type source contributions in seismic hazard assessment

The approach proposed by Rivas-Medina et al. (Nat Hazards Earth Syst Sci 18:2809–2823, 2018. https://doi.org/10.5194/nhess-18-2809-2018 ) integrates fault-type and zone-type sources for seismic hazard assessment. However, its practical implementation faced convergence issues caused by uncertainties in user-defined parameters such as the maximum completeness magnitude ( MmaxC ) and the β-value of the zone-type source (btz). This study presents an improved version of the methodology, referred to as the HybridModel (HM), which addresses these limitations through an iterative procedure that systematically identifies parameter combinations balancing the seismic potential derived from the seismic catalog with the tectonic moment rates associated with mapped active faults. The HM is implemented through a Python and RStudio-based tool that facilitates the exploration of multiple solutions, their incorporation into logic trees, and the explicit treatment of epistemic uncertainties. Applications in southern Spain and the Northern Transverse Strip of Guatemala demonstrate the versatility of the HM in different tectonic contexts and its capability to generate realistic seismic hazard estimates. Overall, the HM provides a practical and robust framework for integrating faults into seismic hazard assessment while reducing reliance on subjective parameter choices.