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Ground-Motion Characterization of Puerto Rico and the U.S. Virgin Islands for the 2025 Update of the USGS National Seismic Hazard Model

Description: 

We assess ground-motion models (GMMs) developed for shallow crustal faulting or subduction zones for application in Puerto Rico and the U.S. Virgin Islands as part of the 2025 update of the U.S. Geological Survey (USGS) National Seismic Hazard Model. We present preliminary analysis of GMM performance, including for site response, using linear mixed-effects regression. For our analysis we used the USGS software gmprocess to compile a dataset with over 8000 ground-motion records since 2006 from 888 earthquakes with magnitudes ranging from 4.0 to 6.5 and depths reaching up to 200 km; more than half of the ground motions were recorded since January 2020. We use the USGS SeismoTectonic Regime Earthquake Calculator (STREC) and the USGS Slab-2 subduction zone geometry model to associate ground motions with either subduction zone or shallow crustal earthquakes. We compute within-event residuals using linear mixed-effects regressions relative to Next Generation Attenuation West2 (NGA-West2) and East (NGA-East) GMMs for shallow crustal earthquakes and NGA Subduction (NGA-Sub) GMMs for subduction zone earthquakes. We consider both measured and proxy values for the time-averaged shear wave speed in the top 30 m (Vs30) when computing site terms for the GMMs. For each GMM, we examine trends with predictive variables, such as earthquake magnitude and rupture distance, and the overall bias values. Future work will likely leverage Sammon mapping to provide a more quantitative basis for assigning weights to the epistemic uncertainty logic tree for GMMs.

Session: The 2023 USGS National Seismic Hazard Model and Beyond - III

Type: Oral

Date: 5/1/2024

Presentation Time: 02:15 PM (local time)

Presenting Author: Brad

Student Presenter: No

Invited Presentation: 

Authors