Abstract:

Database of Geotechnical Shear-Wave Seismic-Velocity Profile Measurements for California and Nevada

Louie, John, Nevada Seismological Laboratory, University of Nevada, Reno, louie@seismo.unr.edu; Alexander R. Simpson, arsimpson@nevada.unr.edu; Jacob Ortega, jacobortega@nevada.unr.edu (Poster)

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 571 sites in Nevada and California, and 40 in New Zealand, using the ReMi technology. The US Geological Survey sponsored many of these measurements, calibrating stations in regional earthquake-monitoring and strong-motion networks. The Google Drive link https://drive.google.com/open?id=15VSI4vhzPfy_GVoB_XYK- sWfrhPM9u5E9, also accessible from https://Louie.pub, leads to a directory structure grouping the measurements by region, and the files are often named with a monitoring network station name. Earthquake- monitoring stations are often on bedrock; the database also includes the results of transects across the Reno, Las Vegas, and Los Angeles urban basins that are mostly deep soil sites. Each file is a self-explanatory, plaintext list of the data and results from the measurement. Measurements made at slightly different ReMi array locations, at different times, and by different interpreters produced multiple files for some sites. The multiple results express both the aleatory variation of velocity in the ground, and the epistemic variability of the measurement technique. 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. 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/. 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/ (select the “Seismic” map type).

Bio:

Professor John N. Louie has been active in exploration seismology and geotechnical research and education since 1982. He has been teaching at UNR for 28 years, sponsoring and advising 25 M.S. and Ph.D. graduates. Prof. Louie invented the “refraction microtremor” shear-wave velocity measurement technique. SeisOpt® ReMi™ services have been available commercially from Optim Earth since 2004. The results of Prof. Louie’s largest project, a three-year program of over 10,000 ReMi™ measurements in Clark County, appeared in 2017 in the Bulletin of the Seismological Society of America.  His website is https://Louie.pub.

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