Vancouver’s building codes may underplay seismic hazard

Vancouver, Canada’s third largest metropolitan area, has the country’s highest seismic risk.

Recent simulations suggest that existing models used to develop current building codes have underestimated the region’s seismic hazard, according to a new study led by researchers from the University of British Columbia. Vancouver is surrounded by mountains and lies in a basin composed of deep sedimentary deposits near the Cascadia Subduction Zone, an active tectonic plate boundary.

This geology is softer and less compact than the surrounding bedrock, and will amplify shaking caused by seismic waves, researchers say. This makes high-rises in the city more vulnerable to damage from a major earthquake than in other regions.

Ground motion models serve as the foundation for Canada’s national seismic hazard model, and they typically rely on past observations of earthquakes from around the world. Seismic codes are based on these, but do not account for Vancouver’s particular geology. Tall buildings constructed before 1990 are most at risk.