Objectives
The nearly completed NGA-East project has developed ten ground motion models (GMMs) applicable to hard reference rock conditions in Central and Eastern North America (CENA). Applicable to a reference site condition having a shear wave velocity of 3.0 km/s and high-frequency diminutive parameter kappa = 0.006 sec, these GMMs provide median estimates of pseudo-spectral accelerations (PSAs) across a range of magnitudes (generally M 3 to 8) and distances (generally 0 to 1000 km) that are needed for probabilistic seismic hazard analysis for national map and site-specific applications. However, mean estimates of ground motions are also needed for soil conditions not conforming to the hard rock 3.0 km/s shear wave velocity.
A number of CENA-specific site amplification models currently exist to, in conjunction with a hard-rock conditioned GMM, provide estimates of ground motions for soil conditions. The objective of this project is to form an expert panel to review alternate site amplification models and provide recommendations to USGS (and other interested parties) regarding the estimation of site effects in CENA. This input will be useful for the development of the next version of the USGS seismic hazard maps, which are anticipated to include ground motion estimates for various soil site conditions (not just reference rock at the B/C boundary).
