Towards a Spatial Probabilistic Submarine Landslide Hazard Model for Submarine Canyons

The Cook Strait Canyon of central New Zealand was identified as a priority area to quantify landslide-generated tsunami hazard in a national study in 2005. Therefore the canyon system has seen increasing research interest over the last decade. Landslide scars have been mapped throughout the whole of the Cook Strait Canyon area and analysis of landslide morphology demonstrates that the majority of landslides have some dependence on the topography of the canyon system. Axial downcutting destabilising lower canyon walls is proposed as the principal factor preconditioning slopes for failure. The canyons occur in an active tectonic environment and earthquakes are inferred to be the overriding failure triggering mechanism. To develop an underpinning magnitude frequency model for probabilistic landslide-tsunami hazard assessment we have created a Monte Carlo based framework to assess the spatial distribution earthquake triggered slope stability within the canyon. The framework is object-oriented and the individual components required to calculate slope stability are implemented in a modular fashion. We drive the model using a long term synthetic earthquake catalogue based on known earthquake parameters for upper-plate and subduction zone fault sources. It is using an empirically derived landslide volume distribution for the Cook Strait Canyon. The model predicts about 1.35 potential slope failures in the Cook Strait Canyon over a period of 500 years with a volume exceeding 0.1 km(3).