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journal article Open Access Apr 09, 2026

Suitability of Ground‐Motion Models for Seismic Hazard Assessments in Puerto Rico and the US Virgin Islands

Brad T. Aagaard ORCID Morgan P. Moschetti Kyle B. Withers
Earthquake Spectra Vol. 42 No. 2 · Wiley
View at Publisher Save 10.1002/esp4.70047
Abstract
We perform linear mixed‐effects analyses with a ground‐motion dataset to evaluate how well ground‐motion models (GMMs) fit active crustal, subduction interface, and subduction intraslab earthquakes in Puerto Rico and the US Virgin Islands. Most of the GMMs reproduce the spatial variation in peak ground motions with earthquake magnitude and rupture distance but predict ground motions 0.3–1.0 natural log units (35%–270%) greater than observations. Two GMMs developed for Puerto Rico that are based on ground‐motion records from mostly magnitude 4–5 earthquakes do not perform as well. We attribute the period‐dependent overprediction in observed ground motions to differences between the observed site response and the linear site response in the GMMs. Consequently, we developed region‐specific GMMs by adjusting the period‐dependent linear site response coefficients and period‐dependent constant coefficients to remove most of the bias between predicted ground motions and observations. For the analysis, we compile ground‐motion records and process waveforms to build a dataset with 10,127 records at 72 stations from 849 magnitude 4.0–6.4 earthquakes between 1 January 2006 and 31 March 2024. The earthquakes include active crustal, subduction interface, and subduction intraslab events. We evaluate the GMMs using the time‐averaged shear wave speed in the top 30 m (), which we compile from site surveys and proxy values computed from horizontal to vertical spectral ratios. Site terms exhibit strong consistency across GMMs and crustal and subduction earthquakes, indicating that the linear mixed‐effects analysis successfully isolates the effects of local site response. The event terms show little spatial correlation and more substantial variability than in other regions, which we attribute to uncertainties in the earthquake magnitudes. This analysis guides the selection of the GMMs for the 2025 update of the National Seismic Hazard Model for Puerto Rico and the US Virgin Islands.
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Citations
86
References
Details
Published
Apr 09, 2026
Vol/Issue
42(2)
License
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Authors
B
Brad T. Aagaard

Geologic Hazards Science Center U.S. Geological Survey Golden Colorado USA

M
Morgan P. Moschetti

Geologic Hazards Science Center U.S. Geological Survey Golden Colorado USA

K
Kyle B. Withers

Geologic Hazards Science Center U.S. Geological Survey Golden Colorado USA

Cite This Article
Brad T. Aagaard, Morgan P. Moschetti, Kyle B. Withers (2026). Suitability of Ground‐Motion Models for Seismic Hazard Assessments in Puerto Rico and the US Virgin Islands. Earthquake Spectra, 42(2). https://doi.org/10.1002/esp4.70047
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