Gridded Seismicity Models for the 2025 USGS National Seismic Hazard Model for Puerto Rico and the U.S. Virgin Islands
Description:
Gridded (or background) seismicity models are a critical component of probabilistic seismic hazard assessments, accounting for off-fault and smaller magnitude earthquakes. They are typically developed by declustering and spatially smoothing an earthquake catalog to estimate a long-term seismicity rate that can be used to forecast future earthquakes. Here, we present new gridded seismicity models for use in the 2025 National Seismic Hazard Model (NSHM) for Puerto Rico and the U.S. Virgin Islands (PRVI). The previous PRVI NSHM was released in 2003, and so our new models incorporate updates to both data and methodology. We utilize an updated earthquake catalog based on improved Puerto Rico Seismic Network data with newly characterized completeness epochs. The catalog is divided into crustal, subduction interface, and intraslab seismicity using new methods and an updated subduction zone geometry. We consider three declustering methods: Gardner and Knopoff (BSSA, 1974; also used in the 2003 model), Reasenberg (JGR, 1985) and the nearest-neighbor method of Zaliapin and Ben-Zion (JGR, 2020). To spatially smooth the catalogs, we employ two-dimensional Gaussian kernels of either fixed or adaptive (variable) bandwidth (Frankel, SRL, 1995; Helmstetter et al., SRL, 2007; Moschetti, BSSA, 2015). The spatial probability density functions that result from declustering and smoothing are later combined with a rate model developed using the new methodology applied to the 2023 U.S. NSHM 50-state update (Petersen et al., Earthquake Spectra, 2023), which improves representation of epistemic uncertainty relative to the 2003 model. We present preliminary PRVI gridded seismicity models and examine how they are impacted by the ongoing and extraordinarily active Southwest Puerto Rico sequence.
Session: The 2023 USGS National Seismic Hazard Model and Beyond [Poster Session]
Type: Poster
Date: 5/1/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Andrea
Student Presenter: No
Invited Presentation:
Authors
Andrea Llenos Presenting Author Corresponding Author allenos@usgs.gov U.S. Geological Survey |
Andrew Michael ajmichael@usgs.gov U.S. Geological Survey |
Allison Shumway ashumway@usgs.gov U.S. Geological Survey |
Kirstie Haynie khaynie@usgs.gov U.S. Geological Survey |
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Gridded Seismicity Models for the 2025 USGS National Seismic Hazard Model for Puerto Rico and the U.S. Virgin Islands
Session
The 2023 USGS National Seismic Hazard Model and Beyond