Shallow Shear-Wave-Velocity Data

The shear-wave-velocity (Vs) database was originally compiled for the site-response map of Salt Lake Valley (Ashland and Rollins, 1999) and later updated for the shear-wave-velocity/site-conditions map of the Wasatch Front urban corridor (McDonald and Ashland, 2008).

Mean Vs calculated for the upper 30 m (Vs30) of a profile is used to define soil site classes by the International Building Code (IBC). We expanded the Vs30 database beyond Salt Lake County to include data along the rest of the Wasatch Front, although data outside Salt Lake County are sparse.

The database includes shear-wave-velocity measurements only to depths of 30 m or greater, measured directly using downhole, cone penetrometer (CPT), and Rayleigh-wave inversion/SASW (spectral analysis of surface waves) methods. No data shallower than 30 m, standard-penetration tests (SPT), or undrained shear-strength conversions are included. A database summary table includes Vs30 values calculated using Equation 16-40 in the 2006 IBC.

The summary table of the database is downloadable as an Excel spreadsheet that contains general location and source information as well as Vs30, engineering-geologic unit, and IBC site-class information keyed to the McDonald and Ashland (2008) site-conditions map.

In many cases, location coordinates are not precise and may represent a general site locality rather than individual test locations. Shear-wave-velocity data for individual tests are available as downloadable scans in Adobe PDF format of graphic and/or tabulated logs and supplemental information, including lithologic logs and geotechnical laboratory testing data where available.

References

Ashland, F.X., and Rollins, K., 1999, Seismic zonation using geotechnical site-response mapping, Salt Lake Valley, Utah: Unpublished Final Technical Report to the U.S. Geological Survey, NEHRP Contract No. 1434-HQ-97-GR-03126, 31 p.

McDonald, G.N., and Ashland, F.X., 2008, Earthquake site conditions in the Wasatch Front urban corridor, Utah: Utah Geological Survey Special Study 125, 1 pl. scale 1:50,000, 41 p., CD.