Additional Period and Site Class Maps for the 2018 USGS National Seismic Hazard Model

Date: 4/24/2019

Time: 08:45 AM

Room: Pike

The updated 2018 National Seismic Hazard Model (NSHM) includes new ground motion models (GMMs) and soil amplification factors for the central and eastern U.S. (CEUS) and the incorporation of basin depths from local seismic velocity models in the western U.S. (WUS). These additions allow us, for the first time, to calculate seismic hazard for an expanded set of spectral periods (0.01s to 10s) and site classes (V_S30 = 2,000 m/s to 150 m/s) for the conterminous U.S., as well as account for amplification of long-period ground motions in deep sedimentary basins in the Los Angeles, San Francisco Bay, Salt Lake City, and Seattle regions. The availability of the new soil amplification factors in the CEUS has also allowed us to produce a variable V_S30 map for the conterminous U.S. In order to calculate hazard for these additional periods and site classes we updated our GMM criteria to state that GMMs need to be valid for the range of spectral periods and site classes in which we calculate hazard. In addition, the WUS subduction GMMs were modified to be able to use basin depths from the local seismic velocity models. The additional period and site class maps for the 2018 NSHM will be compared to the maps for the 2014 NSHM, and differences will be discussed. The maps will be submitted to the Building Seismic Safety Council for consideration in the development of the next-generation of seismic design value maps.

Presenting Author: Peter Powers

Authors