Assessing Site Characterization in Puerto Rico: Towards the 2025 Update of the Puerto Rico and Virgin Islands Portion of the USGS National Seismic Hazard Model
Description:
The U.S. Geological Survey (USGS) will update the Puerto Rico and Virgin Islands portion of the National Seismic Hazard Model (NSHM) in 2025, following on the 2023 50-State NSHM update. Part of the update will include evaluation of empirical ground-motion models (GMMs) used for both shallow crustal and subduction-zone sources using an updated ground-motion data set. As an early step towards understanding regional ground motion effects, we compile the time-averaged shear-wave velocities in the upper 30 meters (VS30) from measurements at sites where they are available, and assign proxy-based values elsewhere. Two spatially varying VS30 maps are used in the latter case: one based on a topographic slope proxy, and one based on a proxy that combines a database of VS30 measurements in the U.S. with a suite of remotely sensed geospatial parameters using machine learning. These proxies are compared with recently measured VS30 values at 20 stations in PR to assess their efficacy. We also investigate horizontal-to-vertical spectral ratios (HVSRs) from ambient noise recorded at seismic stations across the island, towards the development and improvement of existing site response models in GMMs. An automated HVSR peak-picking algorithm identifies the dominant frequencies (fd) and amplitudes of peaks and fits a Gaussian pulse function when peaks are present. These new site characterization data will: (1) help determine how the ergodic GMMs developed using global databases, and their respective site-amplification models conditioned on VS30, perform in Puerto Rico; and (2) allow us to look towards developing new site response models using fd, and compare these models with those in existing GMMs.
Session: 2025 Puerto Rico and the U.S. Virgin Islands National Seismic Hazard Model Update
Type: Oral
Date: 4/18/2023
Presentation Time: 05:30 PM (local time)
Presenting Author: Sean K. Ahdi
Student Presenter: No
Invited Presentation:
Authors
Sean Ahdi Presenting Author Corresponding Author sahdi@usgs.gov U.S. Geological Survey |
Haiyang Kehoe hkehoe@usgs.gov U.S. Geological Survey |
William Stephenson wstephens@usgs.gov U.S. Geological Survey |
Oliver Boyd olboyd@usgs.gov U.S. Geological Survey |
Morgan Moschetti mmoschetti@usgs.gov U.S. Geological Survey |
Noah Lindberg nlindberg@usgs.gov U.S. Geological Survey |
Thomas Pratt tpratt@usgs.gov U.S. Geological Survey |
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Assessing Site Characterization in Puerto Rico: Towards the 2025 Update of the Puerto Rico and Virgin Islands Portion of the USGS National Seismic Hazard Model
Category
2025 Puerto Rico and the U.S. Virgin Islands National Seismic Hazard Model Update