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Abstract Landslide risk analysis is a common geotechnical evaluation and it aims to protect life and infrastructure. In the case of sensitive clay zones, landslides can affect large areas and are difficult to predict. Here we propose a methodology to determine the landslide hazard across a large territory, and we apply our approach to the Saint-Jean-Vianney area, Quebec, Canada. The initial step consists of creating a 3D model of the surficial deposits of the target area. After creating a chart of the material electrical resistivity adapted for eastern Canada, we applied electric induction to interpret the regional soil. We transposed parameter values obtained from the laboratory to a larger scale, that is to a regional slope using the results of a back analysis undertaken earlier, on a smaller slide within the same area. The regional 3D model of deposits is then used to develop a zonation map of slopes that are at risk and their respective constraint areas with the study region. This approach allowed us to target specific areas where a more precise stability analysis would be required. Our methodology offers an effective tool for stability analysis in territories characterized by the presence of sensitive clays.

Abstract A seismic microzonation study was conducted to refine the seismic hazard model for the city of Saguenay, Canada. The Quaternary geology underlying Saguenay shows complex glacial and post-glacial stratigraphy with a number of buried valleys filled with fluvioglacial and glaciomarine sediments. High impedance contrast between rock formations and surficial sediments is prone to seismic amplification. To evaluate their applicability, advantages and limitations in capturing the geological specificity of the study area, four site classification methods were applied: the current National Building Code of Canada (NBCC) and Eurocode 8, both mainly based on the average shear-wave velocity for the surficial sediments (V S,avg ) and for the top 30 m (V S,30 ); a method based on the fundamental site period (T 0 ); and a hybrid method based on the combination of V S,30 , T 0 and V S,avg . The study specifically aimed to evaluate the importance of the site classification parameters on the resulting microzonation maps. V S,30 is capable to present the geological and geotechnical site conditions, however, the results may be further improved by considering V s,avg in shallow and T 0 in thick layers of soil sediments as secondary parameters. The T 0 method gives also satisfactory results with T 0 showing a better correlation to V s,30 than to V s,avg . The versatile hybrid method may be challenging to apply in certain cases with its nine different site categories and parameters.