Subsurface Shear Wave Velocity Characterization Using P-Wave Seismograms in Central and Eastern North America

Abstract

The time-averaged shear ( S) wave velocity in the upper 30 meters of sediment ( V S30) is a widely used site parameter for ground motion prediction. When unavailable from measurements, as is often the case at accelerograph stations in Central and Eastern North America (CENA), V S30 is typically estimated from proxies. We propose an alternative for CENA based on a theoretical relationship between S-wave velocity and the ratio of radial to vertical components of the compressional ( P)-wave–dominated portion of the velocity time series. This method is applied to 31 CENA accelerograph sites having measured S-wave velocity profiles. Time-averaged S-wave velocities to depth z ( V SZ) from the proposed method agree well with those from measurements. We develop linear relationships between V SZ and V S30 using CENA S-wave velocity profile data. Values of V S30 established from the proposed method (including depth extrapolation) have lower dispersion relative to data ( σln V = 0.43) than do estimates from available CENA proxies.

VS30 Characterization of Texas, Oklahoma, and Kansas Using the P-Wave Seismogram Method

“…The particle velocities _ U R and _ U Z can be retrieved from recorded velocity time series or integration of recorded acceleration time series with the horizontal components rotated to the direction of the azimuth between the earthquake epicenter and the seismic station. Kim et al (2016) used the initial portions of the time series to select the first peak value of ( _ U Z ) and then the corresponding value of ( _ U R ) at the same moment in time. Kim et al (2016) estimated the ray parameter, p, by assuming a simplified two-layer crustal velocity model, as shown in Figure 1b: E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 5 ; 6 2 ; 2 7 7…”

“…Kim et al (2016) used the initial portions of the time series to select the first peak value of ( _ U Z ) and then the corresponding value of ( _ U R ) at the same moment in time. Kim et al (2016) estimated the ray parameter, p, by assuming a simplified two-layer crustal velocity model, as shown in Figure 1b: E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 5 ; 6 2 ; 2 7 7…”

“…V P 1 , V P 2 , and D 1 are obtained based on an assumed crustal velocity model. To apply the P-wave seismogram proxy method, Kim et al (2016) utilized the crustal velocity models developed by the Electric Power Research Institute (EPRI) for CENA (EPRI 1993).…”

Estimation of Time‐Averaged Shear Wave Velocity (SWV) to 30 m considering Site SWV Structural Characteristic

“…Developing site factors has been done by compiling ground motion data recorded at soil and rock sites during past earthquakes and examining dependence of amplification factor on certain site parameter, also known as site proxy [1]. Given that the site shallow SWV is a determining factor of the effect of the local site condition [11][12][13], the most commonly used site proxy is the timeaveraged SWV to 30 m, V S30 .…”

Aleatory Variability and Site Effects: The Problem of Soil Classification

“…The SRA has been performed adopting two different procedures, differing for assumed hypotheses, computational effort and results reliability [14]. The first one [15], working in the frequency domain, performs one-dimension linear-elastic and equivalent-linear (SHAKE type) site response analysis using time series theory ground motions.…”