Regional National Earthquake Hazards Reduction Program (NEHRP) soil class maps have become important input parameters for seismic site characterization and hazard studies. The broad range of shallow shear-wave velocity (VS30, the average shear-wave velocity in the upper 30 m) measurements in the St. Louis area results in significant uncertainties between the actual spot values and the averaged values used to assign NEHRP soil classes for regional seismic hazard studies. In the preparation of an NEHRP site classification map of the St. Louis urban area, we analyzed 92 shear-wave velocity (VS) measurements, supplemented by 1400+ standard penetration test (SPT) profiles in areas bereft of VS measurements. SPT blow counts correlated to VS values based on the published correlations. The data were then compiled for respective surficial geologic units and bedrock type. These data suggest that the reciprocal of VS30 exhibits a fairly linear relationship with depth to bedrock, likely because VS30 is a function of the thickness of surficial materials exhibiting relatively low VS values. The VS30 values were interpolated by summing the regressed VS30 on the depth to bedrock and kriged values of the regression residuals. The resulting NEHRP site classification maps predict that upland areas of the St. Louis area are spatially classified as soil site classes SB to SD, while the low-lying floodplains are consistently classified as SD to SF.
J. Chung and J. D. Rogers, "Seismic Site Classifications for the St. Louis Urban Area," Bulletin of the Seismological Society of America, vol. 102, no. 3, pp. 980-990, Seismological Society of America, Jun 2012.
The definitive version is available at http://dx.doi.org/10.1785/0120110275
Geosciences and Geological and Petroleum Engineering
Keywords and Phrases
AS-Soils; Earthquake Hazard; Flood-Plains; Geologic Units; Input Parameter; Linear Relationships; Regression Residuals; Seismic Hazards; Seismic Sites; Shear-Wave Velocity; Site Classification; Soil Class; Standard Penetration Test; Upland Area; Urban Areas; Uncertainty Analysis; Bedrock; S-Wave; Missouri; Saint Louis; United States
St. Louis, Missouri
International Standard Serial Number (ISSN)
Article - Journal
© 2012 Seismological Society of America, All rights reserved.