Development of seismic hazard maps for the proposed 2005 edition of the National Building Code of Canada

Abstract

A new seismic hazard model, the fourth national model for Canada, has been devised by the Geological Survey of Canada to update Canada's current (1985) seismic hazard maps. The model incorporates new knowledge from recent earthquakes (both Canadian and foreign), new strong ground motion relations to describe how shaking varies with magnitude and distance, the newly recognized hazard from Cascadia subduction earthquakes, and a more systematic approach to reference site conditions. Other new innovations are hazard computation at the 2% in 50 year probability level, the use of the median ground motions, the presentation of results as uniform hazard spectra, and the explicit incorporation of uncertainty via a logic-tree approach. These new results provide a more reliable basis for characterizing seismic hazard across Canada and have been approved by the Canadian National Committee on Earthquake Engineering (CANCEE) as the basis of the seismic loads in the proposed 2005 edition of the National Building Code of Canada.Key words: seismic hazard, earthquake, probability, uniform hazard spectrum, maps, Cascadia subduction, strong ground motions, uncertainty, CANCEE, National Building Code of Canada.