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TitleCrossing the Border Again: Assessing the differences between Canada's 2015 and the United States' 2014 seismic hazard maps
AuthorHalchuk, S; Adams, JORCID logo; Petersen, M; Rogers, G; Allen, T I
SourceProceedings of the Canadian Conference on Earthquake Engineering 2015, 2015 p. 1-10
Alt SeriesEarth Sciences Sector, Contribution Series 20150125
PublisherCanadian Association for Earthquake Engineering
Meeting11th Canadian Conference on Earthquake Engineering; Victoria; CA; July 21-24, 2015
File formatpdf
ProvinceBritish Columbia; Alberta; Saskatchewan; Manitoba
NTS62E; 62F; 72E; 72F; 72G; 72H; 82E; 82F; 82G; 82H; 92B; 92C; 92E; 92F; 92G; 92H
AreaWeyburn; Lethbridge; Kallispell; Cranbrook; Kelowna; Vancouver; Port Angeles; Victoria; Nanaimo; Canada; United States of America
Lat/Long WENS-125.0000 -101.0000 50.0000 48.0000
Subjectsgeophysics; earthquakes; earthquake studies; earthquake magnitudes; earthquake catalogues; earthquake mechanisms; earthquake foci; seismic risk; seismic interpretations
Illustrationslocation maps; tables
ProgramCanadian Hazard Information Service
Released2015 01 01
AbstractThe Geological Survey of Canada¿s new suite of seismic hazard maps were prepared for the seismic design codes in the year 2015 edition of the National Building Code of Canada (NBCC). The United States Geological Survey (USGS) has released a similar set of maps in 2014 covering the conterminous United States for the National Earthquake Hazards Reduction Program (NEHRP). The 2015 NBCC maps now adopt a fully probabilistic model that provides mean hazard values consistent with the approach used by the USGS. This provides an improved basis for comparing the two national models. Correcting for differences in the reference site condition [class C (Vs30 = 450 m/s) in Canada and the B/C boundary (760 m/s) in the United States], there is general agreement in the pattern of hazard and relative hazard levels, as shown by comparing values between Canadian and appropriate U.S. cities and examining border-region maps. However, hazard contours do not necessarily match across the border. Differences in the definition of source zones, choice of ground motion prediction equations, and mode of incorporating Cascadia subduction earthquakes all contribute to these cross-border differences.
Summary(Plain Language Summary, not published)
Both the Geological Survey of Canada and the United States Geological Survey have recently completed updates to the models which estimate the expected earthquake shaking in their respective countries. These shaking values are used in the national building codes to help define the design requirements for earthquake resistant structures. Despite differences in model inputs, hazard calculation programs, and philosophy, there is generally good similarity in the level and pattern of seismic hazard across the Canada-U.S. border. Understanding these differences will lead to closer harmonization in the methods used by the two agencies.

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