Geotechnical investigations of an earthquake that triggered disastrous landslides in eastern Canada about 1020 cal BP

Geotechnical studies are carried out to investigate the location and magnitude of a prehistoric earthquake in eastern Canada. Previous studies identified 12 sensitive clay landslides of about 1020 cal BP in the Ottawa-Gatineau region, including one of the most disastrous slope failures in eastern Canada. The landslides were hypothesized to have been triggered by an earthquake. In the current study, three of those landslides are investigated to understand their failure mechanisms. The study sites form a triangle of lateral distances of about 38, 38 and 35 km. Micro-seismic surveys, cone penetrometer tests, vane shear tests, soil sampling and laboratory testing are conducted to collect geotechnical data. Slope stability models are constructed to calculate threshold ground accelerations required to trigger the landslides. The ground accelerations are used with Ground-Motion Prediction Equations to triangulate the earthquake. The results indicate an earthquake of a minimum moment magnitude of 5.9 near Eardley, Quebec.