Integrating geodetic constraints from major faults and the subduction zone into probabilistic seismic hazard assessments (PSHA) for Guatemala

Advances in geodetic observations provide new opportunities to improve long-term earthquake forecasting and probabilistic seismic hazard assessment (PSHA) by complementing the limited temporal coverage of earthquake catalogs. Guatemala is a highly seismic country located at the complex interaction of the North America, Caribbean, and Cocos plates, where both subduction and major crustal fault systems contribute to seismic hazard. In this study, we integrate geodetic constraints from the subduction zone and the main strike-slip faults, including the Polochic-Chixoy, Motagua, and Jalpatagua fault systems, into a geodetic-informed PSHA framework. Geodetically derived slip rates and interplate coupling are used to approximate seismic moment rate budgets and magnitude-frequency distributions for interplate and upper-plate sources. Multiple approaches are explored to estimate earthquake rates and maximum magnitudes, accounting for epistemic uncertainties (e.g., slip-rate models, fault segmentation, catalog declustering, rupture scaling). These alternative source characterizations are implemented within a logic tree and incorporated into a modified 2025 KUKAHPAN seismic hazard model (KASHM 2025), including fault-type sources and revised interplate recurrence parameters. Our hazard computations show that near major faults, predicted peak ground accelerations increase by more than 20% compared with classical zoned-based models, especially along fault systems with high slip rates (Motagua and Jalpatagua faults). In contrast, differences for interplate sources remain within the epistemic uncertainty of the reference model, due to the distance of the interface from the Guatemalan mainland. We quantify the fault distance-dependent effect by estimating aggravation factors derived from the ratio between our geodetic model and the KASHM 2025. Fault segments classified as very high seismic potential (slip rate > 8 mm/yr and M _max > 7.0) show strong hazard increase persisting up to ~ 55 km, while high seismic potential faults (slip rate ≤ 8 mm/yr and M _max ≤ 7.0) exhibit increases that decays within ~ 45 km. Finally, we propose an integrated seismic hazard map combining classical and geodetic-based approaches, highlighting the complementarity of seismic and geodetic data. Our findings emphasize the importance of fault slip rates and subduction coupling, and provide near-fault aggravation equations as a practical tool for site-specific PSHA and building codes.