Correlating Resonance Frequency From Hvsr With Vs30 Along the Wasatch Fault, Northern Utah, USA
Description:
The Wasatch Fault Corridor of northern Utah has an increasingly high seismic risk due to rising population density. Vs30 (time-averaged subsurface shear-wave velocity for the upper 30 meters) is the key parameter to determine how a site will respond to earthquake shaking; however, finding Vs30 usually requires an intensive array-based measurement with an active seismic source. The horizontal to vertical spectral ratio (HVSR) single-sensor technique is passive, unintrusive, and more convenient, potentially allowing for rapid assessment if a transformation can be obtained between Vs30 and the fundamental resonance frequency (f0) provided by the HVSR for the shallowest stratigraphic layers. The purpose of our study is to evaluate the effectiveness of correlating the Vs30 with HVSR f0 to either supplement or replace Vs30 measurements. Reoccupying previously surveyed Vs30 sites in Utah County, Utah, we measured the f0 using HVSR with a three component TROMINO seismometer. The sites are located on the hanging wall (west) of the Wasatch fault zone amongst alluvial and lacustrine Quaternary sediments. For each site, we recorded ambient noise for 20 minutes and computed the amplitude frequency spectra for the three components (N-S, E-W (“H”), up-down (“V”)), then converted these to H/V response as a function of frequency, from which we observed the f0 of the site by choosing the highest H/V spectral peak. The f0 ranged between 0.28 and 1.09 Hz for all sites. To produce the best transformation of Vs30 to f0, we selected those measurements for which the lowest-frequency prominent H/V peak was observed within the spectrum. Sixteen out of the 23 measurements were selected due to their well-expressed H/V spectral peaks and lower uncertainties. The linear regression between Vs30 as a function of f0 resulted in a moderate positive correlation. Further work will include collection of more HVSR measurements to increase the accuracy of our study.
Session: Regional-Scale Hazard, Risk and Loss Assessments [Poster Session]
Type: Poster
Date: 5/3/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Kate
Student Presenter: Yes
Invited Presentation:
Authors
Kate Smith Presenting Author Corresponding Author smithk86666@gmail.com Brigham Young University |
John McBride john_mcbride@byu.edu Brigham Young University |
Ron Harris rharris@byu.edu Brigham Young University |
Bo Worthen boworthen@icloud.com Brigham Young University |
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Correlating Resonance Frequency From Hvsr With Vs30 Along the Wasatch Fault, Northern Utah, USA
Category
Regional-Scale Hazard, Risk and Loss Assessments