Shear-wave velocity site characterization in Oklahoma from joint inversion of multi-method surface seismic measurements: Implications for central U.S. Ground Motion Prediction

Bulletin Seismological Society America
By: , and 

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Abstract

We analyze multimethod shear (SH)‐wave velocity (VS) site characterization data acquired at three permanent and 25 temporary seismograph stations in Oklahoma that recorded M 4+ earthquakes within a 50 km hypocentral distance of at least one of the 2016 M 5.1 Fairview, M 5.8 Pawnee, or M 5.0 Cushing earthquakes to better constrain earthquake ground‐motion modeling in the region. We acquired active‐source seismic data for time‐averaged VS to 30 m depth (VS30) at 28 seismograph stations near the Fairview, Pawnee, and Cushing epicentral areas. The SH‐wave refraction travel times coupled with Rayleigh‐ and Love‐wave phase velocity dispersion were extracted and modeled in a nonlinear least‐squares (L2) joint inversion to obtain a best‐fit 1D VS versus depth profile for each site. At a subset of sites where the preferred L2 inverse model did not optimally fit each of the Love, Rayleigh, and SH travel‐time datasets, we explore application of simulated annealing in a joint inversion to find a more global solution. VS30 values range from 262 to 807  m/s for the preferred measured (in situ) VS profiles, or National Earthquake Hazards Reduction Program (NEHRP) site class D to B, and are broadly comparable with estimates from previous data reports in the region. Site amplification estimates were calculated next from 1D SH transfer functions of the preferred VSVS profiles and then compared against observed horizontal‐to‐vertical spectral ratios (HVSRs) from nearby seismograph stations. We generally see good agreement between the predicted in situ model and the observed HVSR resonant frequencies, with nominal amplifications between 2 and 10 within the 2–15 Hz frequency band. Next, using 40 known in situ VS30 measurements in the region, we demonstrate that the in situ VS30 values improve the fit for selected suites of ground‐motion models (GMMs) for M 4+ earthquakes within a 50 km hypocentral distance when compared with proxy methods, arguing for future development of GMMs implementing in situ VS profiles.

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Publication type Article
Publication Subtype Journal Article
Title Shear-wave velocity site characterization in Oklahoma from joint inversion of multi-method surface seismic measurements: Implications for central U.S. Ground Motion Prediction
Series title Bulletin Seismological Society America
DOI 10.1785/0120200348
Volume 111
Issue 4
Year Published 2021
Language English
Publisher Geological Society of America
Contributing office(s) Geologic Hazards Science Center
Description 20 p.
First page 1693
Last page 1712
Country United States
State Oklahoma
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