Time-averaged shear-wave velocity in the upper 30 m of a site (VS30) is the most common parameter used to characterize seismic site response in ground-motion models. However, in central and eastern North America (CENA), only 6% of the seismic recording stations that contributed data to the Next Generation Attenuation-East (NGA-East) project have measurement-based VS30 values. We describe a shear-wave velocity (VS) measurement database for CENA that was compiled to support the development of proxy-based methods for VS30 estimation. Using this database, we develop a hybrid geology-slope approach for VS30 estimation that utilizes newly considered largescale geologic maps, the extent of Wisconsin glaciation, sedimentary basin structure, and 30 arcsec topographic gradient. Nonglaciated sites have relatively modest natural log dispersion of VS30 (σln V = 0:36) relative to glaciated regions (σln V = 0:66), indicating better proxy-based predictability of VS30 for the former. Based on these findings, we provide estimates of natural logmean and standard deviation of VS30 for NGA-East recording stations in a station database, available in the E electronic supplement to this article.
ASJC Scopus subject areas
- Geochemistry and Petrology