Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon

Earthquake Spectra
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Abstract

We assess how well the Next-Generation Attenuation-West 2 (NGA-West2) ground-motion models (GMMs), which are used in the US Geological Survey’s (USGS) National Seismic Hazard Model (NSHM) for crustal faults in the western United States, predict the observed basin response in the Great Valley of California, the Reno basin in Nevada, and Portland and Tualatin basins in Oregon. These GMMs rely on site parameters such as the time-averaged shear-wave velocity (VS) in the upper 30 m of Earth’s crust (VS30) and depths to 1.0 and 2.5 km/s shear-wave isosurfaces (Z1.0 and Z2.5) to capture basin effects and were developed using observations and simulations primarily from the Los Angeles region in southern California. Using ground-motion records from mostly small-to-moderate earthquakes and mixed-effects regression analysis, we find that the GMMs perform well with our local basin-depth models for the California Great Valley. With our local basin-depth models for Reno, the GMMs do not perform as well for this relatively shallow basin and exhibit little sensitivity to the basin parameters used in the NGA-West2 GMMs. We also find good performance for the local Z1.0 model across the Portland region, whereas the local Z2.5 model provides little predictive power except at sites in the deepest part of the Tualatin basin. Additional work could improve the performance of the site and basin terms in the NGA-West2 GMMs for regions with geologic structure different than the deep basins in southern California and the Great Valley. In addition, we find significant discrepancies among the GMMs in how the uncertainty in the ground motion varies with basin depth and pseudospectral period. Our results can help guide seismic hazard analyses on whether to include these local basin-depth models.
Publication type Article
Publication Subtype Journal Article
Title Empirical ground-motion basin response in the California Great Valley, Reno, Nevada, and Portland, Oregon
Series title Earthquake Spectra
DOI 10.1177/87552930241237250
Volume 40
Issue 2
Year Published 2024
Language English
Publisher Earthquake Engineering Research Institute
Contributing office(s) Earthquake Science Center, Geologic Hazards Science Center - Seismology / Geomagnetism
Description 33 p.
First page 1099
Last page 1131
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