Cross-Border Comparison Between Canada’s 6th Generation and the United States’ 2018 Seismic Hazard Models

Session: Forthcoming Updates of the USGS NSHMs: Hawaii, Conterminous U.S. and Alaska [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Both Natural Resources Canada and the United States Geological Survey have recently updated their estimates of long-term natural seismic hazard with the release of the 6^th Generation Seismic Hazard Model of Canada (CanadaSHM6) and the 2018 National Seismic Hazard Model of the conterminous United States (NSHM18), respectively. In western and eastern North America comparisons are done to distances on the order of 100 km and 200 km from the border, respectively. As expected, there is general agreement in the pattern and level of hazard in the Pacific Northwest, reflecting the fact that both models use comparable ground motion models and the estimates of earthquake rates in regions of high seismicity are reasonably robust (including the rate of Cascadia subduction events). A comparison of seismic hazard values in southeastern Canada and northeastern USA reveals a less-similar pattern and different hazard levels, with CanadaSHM6 generally predicting larger hazard values. These differences are largely attributed to different approaches for seismic source characterization and to differences in the implementation of stable crust ground motion models. In intraplate regions of low to moderate seismicity there is considerable uncertainty in the range of technically defensible models and assumptions used, which leads to differences in estimates of mean seismic hazard. For now, each country’s design codes require the use of their national hazard estimates, and there should be no mix-and-matching with the other country’s hazard estimate.

Presenting Author: Stephen C. Halchuk

Authors