2025 Puerto Rico and U.S. Virgin Islands Long-term National Seismic Hazard Model

Summary

The U.S. Geological Survey is nearing the full release of the 2025 Puerto Rico and U.S. Virgin Islands National Seismic Hazard Model (2025 PRVI NSHM). The first version of the PRVI NSHM was released in 2003 (Mueller et al., 2003, 2010), and therefore, this 2025 update includes over 20 years of updated geologic, geophysical, and engineering data, methods, and models. Updates follow similar efforts performed in the recent 2023 50-state NSHM but also include some new methodology. Updates in the 2025 PRVI NSHM include: 
(1) new crustal fault and geologic deformation models; 
(2) updated modeling of subduction zone geometry, interface faults, and interface deformation; 
(3) new magnitude-area scaling relationships; 
(4) improved fault-source rupture models, including accommodating multi-fault ruptures; 
(5) an updated seismicity catalog including revised data from the Puerto Rico Seismic Network; 
(6) a new earthquake catalog separation process that assigns earthquakes to a tectonic regime; 
(7) revised declustering methods (to distinguish mainshocks from foreshocks and aftershocks), smoothing algorithms, and seismicity rate models; 
(8) a more complete representation of epistemic uncertainties (uncertainty resulting from a lack of knowledge or information, which can theoretically be reduced by more information) in the earthquake rupture forecast model; 
(9) adoption of more recent ground-motion models (GMMs) for both active crustal and subduction sources (interface and intraslab), with adjustments made based on PRVI-specific data; 
and (10) development of GMM epistemic uncertainty and aleatory variability (natural, random uncertainty that cannot be eliminated, even with more information) models specific to PRVI in the ground-motion characterization model. 

The NSHMs are community- and consensus-based models that strive to meet the goal of incorporating the latest data, methods, and models currently available and evaluated to be technically acceptable (Jordan et al., 2023). The 2025 PRVI NSHM has been reviewed by three technical review panels. Long-term time-independent mean hazard calculations were performed on a 0.01o by 0.01o grid for all points in the study region for peak ground velocity and 21 spectral periods with a 5%-damped response, for eight National Earthquake Hazards Reduction Program site conditions, and 2%, 5%, and 10% in 50-years probabilities of exceedance (POEs; return periods of 2475, 975, and 475 years, respectively). In addition, epistemic uncertainty, in the form of selected percentiles, was calculated for a suite of 86 test sites as well as for a courser grid (0.025o by 0.025o) of all points in the study region for limited periods, site conditions, and POEs. The full suite of results can be found in the USGS ScienceBase Catalog (Shumway et al., 2025).

Overview Documentation, Data, and Software

Supporting Documentation:
(Input data, models, and methods)

Review Process Documentation