Ground-motion aleatory-variability models for Puerto Rico and the U.S. Virgin Islands

Earthquake Spectra
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Abstract

I develop independent logic trees for aleatory variability for crustal and subduction-zone (interface and intraslab) earthquakes for seismic hazards analyses in Puerto Rico and the U.S. Virgin Islands (PRVI) from existing suites of ground-motion models (GMMs) and from ground-motion datasets, including a regional PRVI dataset. The aleatory variability models are parameterized using a partially nonergodic partitioning of standard deviation that consists of independently developed between-event (mathematical equation), site-to-site (mathematical equation), and event-corrected single-station (mathematical equation) standard deviation components. The effects of nonlinear site response on aleatory variability are incorporated through additional terms that modify the standard deviation components. Because one goal of this work is to develop independent logic trees for aleatory variability that synthesize the aleatory variability models from GMMs, I make use of the functional forms of the input GMMs. The PRVI dataset contains a limited number of stations with high-quality site metadata and does not contain records from earthquakes with magnitudes greater than 6.1, so I choose not to develop the aleatory variability models from the regional dataset alone. Instead, the standard deviation components from regional ground-motion data are evaluated against the components derived from GMMs and from available global datasets, and regionalized standard deviation components are incorporated where there is evidence that regional effects exhibit substantial differences. The resulting logic trees for aleatory variability consist of models of mathematical equation and mathematical equation that are consistent with semiempirical GMMs for active crustal and subduction-zone regimes, and two alternative models of mathematical equation, including one model that exhibits site-to-site variability informed by PRVI data, with values that exceed global models. The aleatory variability models may be considered in future hazards assessments in PRVI to simplify the hazard calculations, to incorporate regional ground-motion variability effects, and to enable direct logic-tree weighs of aleatory variability.

Suggested Citation

Moschetti, M.P., 2026, Ground-motion aleatory-variability models for Puerto Rico and the U.S. Virgin Islands: Earthquake Spectra, v. 42, no. 1, e70037, 27 p., https://doi.org/10.1002/esp4.70037.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Ground-motion aleatory-variability models for Puerto Rico and the U.S. Virgin Islands
Series title Earthquake Spectra
DOI 10.1002/esp4.70037
Volume 42
Issue 1
Publication Date February 26, 2026
Year Published 2026
Language English
Publisher Wiley
Contributing office(s) Geologic Hazards Science Center - Seismology / Geomagnetism
Description e70037, 27 p.
Country United States
Other Geospatial Puerto Rico, U.S. Virgin Islands
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