Seismic Hazard Estimation in Canada and its Contribution to the Canadian Building Code Implications for Code Development in Countries such as Australia

Abstract

Seismic design provisions of national building codes aim to save lives and reduce losses from future earthquakes. The provisions need to be based on reliable seismic hazard maps, the generation of which is a challenge in low-seismicity regions such as eastern Canada and Australia, and which contain inherently-large uncertainties. A process is needed to incorporate the hazard values into design provisions, and this is best done through continual code improvements occurring within an on-going national code committee. Building codes need to balance the benefits against the costs, and so the improvements are aided by crude risk assessments (to focus the effort where the risk is greatest) together with crude cost-benefit analyses. Most codes become more stringent to match evolving societal goals, and while the cost of increased code requirements may be strongly resisted by some groups, they may also be economically justified (present cost versus future loss). The seismic provisions of national building codes tend to focus on new, engineered “large” buildings but may not provide comparable benefits to new “small” buildings and are unlikely to reduce risk in existing buildings, even though damage to these may represent the major loss in moderate-magnitude urban earthquakes like the 1989 Newcastle earthquake. Additional and different strategies are therefore needed to complement existing code activities.