About Vs(z)

The time-averaged seismic shear-wave velocity from the surface to 30 m (100 ft) depth, defined in the Building Code as Vs30, is in the United States one of the principal determinants of earthquake site-hazard classification. Over the past 20 years the Nevada Seismological Lab and the Applied Geophysics class at the University of Nevada, Reno; and Optim Earth have made shallow (<1 km deep) shear-wave velocity measurements at hundreds of sites in Nevada, California, and New Zealand using the ReMi technology. Many of these measurements were made at stations in regional earthquake-monitoring networks, and sponsored by the US Geological Survey. The Google Drive link leads to a directory structure grouping the measurements by region, and the files are often named with the monitoring network station name. Each file is a self-explanatory, plain-text list of the data and results from the measurement. Where multiple files are given for a particular site, measurements were made at slightly different ReMi array locations, at different times, and by different interpreters; thus expressing both the aleatory variation of velocity in the ground and the epistemic variability of the measurement technique (+/- 15% according to Louie, 2001). Each measurement file includes ReMi array location data, a summary Vs30 value, and a modeled shear-wave-velocity-versus-depth profile. Efforts are underway to add the picked ReMi p-f image and the picked fundamental-mode Rayleigh-wave dispersion-curve data to each file. Many of these measurements have been published in peer-reviewed journal papers and project reports (available in the Preprint Archive from Louie.pub). As well, these archives give additional details on ReMi measurements found in the US Geological Survey's Vs30 archive at https://earthquake.usgs.gov/data/vs30/us/ . All data in this archive are in the public domain, distributed under a Creative Commons CC BY license.

An additional 10,722 Vs30 measurements in Las Vegas and Clark County, Nevada are available from the Clark County GIS system at http://gisgate.co.clark.nv.us/ow/ (under the "hamburger" options menu select the "Seismic" map type). A Pancha et al. (2017) paper describes these measurements.

To apply the ReMi technology to your engineering project, contact Optim Earth at optimsoftware.com. For more information on ReMi applications, take a look at the draft ReMi Chapter of the COSMOS Guidelines document on surface-wave array measurement.