Vs30-Fd Relationship for Measured-Vs30 Stations in the Western United States
Description:
Two important ground motion modeling parameters have been used to account for seismic site effects at network seismic monitoring stations: 1) the time-averaged shear-wave velocity (VS) of the upper 30 m from the ground surface (VS30), derived through VS profiles determined from in situ measurements; and 2) the dominant site frequency (fd), derived from the horizontal-to-vertical spectral ratio of earthquake (eHVSR) or microtremor (mHVSR) ground motions recorded by the single-station method. Using fd from mHVSR as an independent parameter for characterizing site effects in ground motion models (GMMs) is important because—when fd is derived from eHVSR—its use in GMMs may introduce circularity, making the eHVSR-based fd less suitable as an independent parameter. These two indices characterize different aspects of site effects and the effectiveness of using either (or the combination of) indices as site terms is an ongoing research topic; fd, particularly when based on microtremor sources is substantially less costly to determine than in situ VS30. As both indices are known to fundamentally represent seismic site conditions, we regress measured VS30 against fd using available data recorded by stations in the western U.S. The many different methods for computing HVSR may result in varying fd estimates, whereas VS30 methods are relatively better established. We examine possible fd-related biases by using a common set of recordings from each network station and by computing their Fourier amplitude spectrum (FAS), power spectral density (PSD), and response spectrum (RS) based HVSRs. We discuss the pros and cons of the FAS, PSD, and RS approaches to computing fd, then present a relationship between VS30 and fd, and compare the relationship to those proposed in recent studies.
Session: Why Ignore the Structure? Soil-structure Interaction and Site Response at Local and Regional Scales - I
Type: Oral
Date: 4/17/2025
Presentation Time: 10:30 AM (local time)
Presenting Author: Kenneth
Student Presenter: No
Invited Presentation:
Poster Number:
Authors
Alan Yong Corresponding Author yong@usgs.gov U.S. Geological Survey |
Albert Kottke arkk@pge.com Pacific Gas & Electric Company |
Kenneth Hudson Presenting Author Ken@Hudsongeotechnics.com Hudson Geotechnics, Inc. |
Shinichi Matsushima matsushima@sds.dpri.kyoto-u.ac.jp Kyoto University |
William Stephenson wstephenson@usgs.gov U.S. Geological Survey |
Fabian Bonilla luis-fabian.bonilla-hidalgo@univ-eiffel.fr University Gustave Eiffel |
Antony Martin amartin@geovision.com GEOVision, Inc. |
Behzad Hassani Behzad.Hassani@bchydro.com B.C. Hydro |
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Vs30-Fd Relationship for Measured-Vs30 Stations in the Western United States
Session
Why Ignore the Structure? Soil-structure Interaction and Site Response at Local and Regional Scales