68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

CO-SEISMIC LARGE LANDSLIDES IN SENSITIVE CLAY IN EASTERN CANADA, A SEARCH FOR AN INITIATION THRESHOLD

Session: Landslides and Slope Stability VI / Mouvements de terrain et stabilité des pentes VI

Pete Quinn, BGC Engineering (Canada)
Martin Zaleski, BGC Engineering (Canada)

This paper examines the search for a peak horizontal ground acceleration (PGA) threshold for triggering co-seismic landslides in sensitive clay in eastern Canada, with the aim of supporting regional risk assessment using HAZUS. Literature sources document a number of small co-seismic landslides associated with small or moderate earthquakes which produced a PGA between about 0.04 g and 0.15 g at the landslide locations. Two papers describe 46 large, co-seismic, sensitive-clay landslides with measured dates. Many of these are associated with the 1663 Charlevoix M7 earthquake, from which site-specific firm ground PGA can be estimated; these range from about 0.03 g to 0.18 g; the remaining landslides are associated with paleo-earthquakes. A clear PGA threshold for triggering large landslides in sensitive clay cannot be inferred from these available data. Earthquake magnitude and distance appear to provide a somewhat better threshold for co-seismic sensitive clay landslides in the study area.