The Next Generation Attenuation Relationships for Central & Eastern North-America (NGA-East) Geotechnical Working Group (GWG) has presented models for site amplification in Central and Eastern North America that represent a significant change from past practice, which was based on models developed for active tectonic regions. The GWG models are ergodic in their formulation, meaning that they produce an average level of amplification conditional on VS30 and other the site parameters. We illustrate the application of these models to four sites in Texas, South Carolina, Mississippi, and New York City, and compare results with site-specific ground response analyses. The results indicate that substantial advantage is possible when ergodic models conditioned only on VS30 are supplemented with a modular term that produces a peak at one or more site natural periods ( Tnat). The article demonstrates features and limitations of the GWG models for sites in Central and Eastern North America and provides useful recommendations for coupling ergodic and non-ergodic (site-specific) modeling as part of seismic hazard studies.
