Probabilistic assessment of the vulnerability of buildings in seismic regions

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Risk assessment and mitigation of potential natural hazards are critical issues facing most Canadian cities. These tasks require both an accurate prediction of the hazard and a careful evaluation of the vulnerability of buildings despite existing uncertainties. In technical terms, a hazard can be described quantitatively as “the likely frequency of occurrence of an event of a specific intensity in a given area,” whereas vulnerability can be defined as “the conditions determined by physical, social, economic, and environmental factors or processes that increase the susceptibility of a community to the impact of hazards.” Among natural disasters, earthquakes represent a particularly important hazard in certain regions of Canada. Seismic risk management requires a risk analysis that can quantify the negative impacts of an earthquake. Ideally, this analysis should include a process for the probabilistic quantification of impacts. To better assess these risks, this project aims to develop a damage simulator that will assess the vulnerability of buildings found within seismic hazard area. The development of this simulator requires a fairly exact 3-D geological model, an adequate seismic microzonation of the territory, and an appropriate vulnerability assessment of existing infrastructure and buildings. ***The first step of the research project involves developing a 3-D geological model of the territory that provides the basis for establishing regional seismic hazards. This model should include multiple variables including the thickness and the type of surficial deposit layers, the depth and type of bedrock, and groundwater levels. Using the CharlevoixHaute-Côte-Nord region of Quebec as a case study, a 3-D model of surficial deposits will be produced from which we will be able to determine the effect of uncertainties associated with estimating the thickness of surficial deposits from available data that varies in density across the region.***The second step is the microzonation of regional seismic hazards based on existing data for the CharlevoixHaute-Côte-Nord region and some new field measurements carried out as part of this project. Multiple methods have been proposed for determining the soil shear wave velocity; all these methods are affected by uncertainties. This part of the project will focus on the effects of uncertainty vis-à-vis seismic shear wave velocity (Vs) in determining soil classes and seismic risk microzonations.***Based on a building vulnerability function and its uncertainties for the regional building types, the third step will develop a damage simulator that incorporates the applied methodologies for assessing hazard and vulnerability. A probabilistic approach can account for both the variable levels of damage associated with earthquakes and the probability occurrence of each seismic scenario. This damage simulator will represent a decision-support tool for the different actors involved in managing seismic risks.