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TitleNew seismic hazard model for north-western Canada
AuthorAllen, T I; Adams, JORCID logo; Halchuk, S; Rogers, G C
SourceCanadian Association for Earthquake Engineering Newsletter 2015, 13 pages
Alt SeriesEarth Sciences Sector, Contribution Series 20150113
PublisherThe Canadian Association of Earthquake Engineering
Meeting11th Canadian Conference on Earthquake Engineering; Victoria; CA; July 21-24, 2015
File formatpdf
ProvinceBritish Columbia; Yukon; Northwest Territories
NTS94; 104; 75; 85; 96; 105; 95; 115; 86; 97; 106; 116; 107; 117
AreaNorth West Canada
Lat/Long WENS-142.0000 -102.0000 70.0000 56.0000
Subjectsengineering geology; geophysics; tectonics; earthquake damage; earthquakes; earthquake resistant design; earthquake risk; earthquake studies; seismic energy; seismic risk; seismic surveys; faults, thrust; faults, slip; faults, strike
Illustrationsseismic maps; equations; tables; graphs
ProgramPublic Safety Geoscience Western Canada Geohazards Project
AbstractThe Geological Survey of Canada has recently completed national seismic hazard models prepared to underpin the seismic provisions for the 2015 National Building Code of Canada. This process involved reassessment and revision of earthquake sources in the Canadian Arctic, northern British Columbia and adjacent Alaska. Area sources are defined through a multi-tiered approach in a GIS framework. The key thematic layers used to guide the area source boundaries are: historical earthquake epicentres; tectonic elements; gravity and magnetic anomalies; and multi-resolution topography and bathymetry.
For the first time, hazard from crustal faults in Yukon, and adjacent Alaska is calculated based on GPS- and paleoseismic-based slip rates. Maximum magnitude for each fault source is determined from published magnitude-area scaling relations. Hazard along the Queen Charlotte and Fairweather faults is also now predominantly based on crustal deformation rates, with minor contributions to off-fault hazard assessed from historical seismicity. In recognition of the MW 7.8 2012 Haida Gwaii thrust earthquake, we partition the slip between the strike-slip Queen Charlotte fault and the shallow-dipping Haida Gwaii thrust modelled as a subduction source.
A regional tectonic model, supported by GPS deformation rates and earthquake focal mechanisms (Leonard et al., JGR, 2007), suggests that observed northerly motion from Yukon continues to the Beaufort Sea margin. The inferred convergence in the Mackenzie Delta region could manifest itself through infrequent large earthquakes with very few small events. Based on this hypothesis, a new Beaufort-Mackenzie Convergence zone allows for the possibility of seismogenic thrusting (up to MW 7.8) beneath the delta sediments.
Summary(Plain Language Summary, not published)
The Geological Survey of Canada (GSC) is responsible for providing seismic hazard information to key stakeholders with the ultimate aim of safeguarding Canadian citizens from the negative impacts of earthquakes. The proposed national hazard models are intended to form the basis for the seismic provisions of the 2015 edition of the National Building Code of Canada (NBCC). This contribution outlines the rationale behind the development of hazard-model inputs for the Western Canadian Arctic (approximately north of 60°N latitude), as well as the newly-implemented shallow crustal faults for the western margin (excluding Cascadia). For the first time, the hazard from crustal faults in Yukon, and adjacent Alaska is calculated based on GPS- and paleoseismic-based slip rates. The sensitivity of these new model assumptions is evaluated in terms of the resulting ground-motion hazard.

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