VS30 at Three Strong-Motion Recording Stations in Napa and Napa County, California--Main Street in Downtown Napa, Napa Fire Station Number 3, and Kreuzer Lane-- Calculations Determined from S-Wave Refraction Tomography and Multichannel Analysis of Surface Waves (Rayleigh and Love) [open pdf - 13MB]
From the Introduction: "In May 2015, we acquired high-resolution seismic profiles near three strong-motion recording stations in the City and County of Napa, California (fig. 1). These three strong-motion stations recorded 2 horizontal peak ground accelerations (PGAs) ranging from 0.329 g (the acceleration due to gravity at the Earth's surface) to 0.611 g (table 1), among the highest recorded in the Napa area during the August 24, 2014, moment magnitude (Mw) 6.0 South Napa earthquake. Our goal was to evaluate the seismic velocities of the underlying geologic material at the strong-motion sites using P- and S-wave refraction tomography and analysis of surface waves and to evaluate time-averaged shear-wave velocities (VS) in the upper 30 meters (m) of the subsurface (VS30) at the sites using methods similar to those used by Catchings and others (2018). In this report, we present results from the three sites--Downtown Napa and Napa Fire Station Number 3, both within the City of Napa, and at the intersection of 4th Avenue and Kreuzer Lane in Napa County."
Open-File Report 2018-1161
United States Geological Survey: https://www.usgs.gov/