Abstract Multibeam echosounder (MBES) images, 3.5 kHz seismic-reflection profiles and piston cores obtained along the southern Queen Charlotte Fault Zone are used to map and date mass-wasting events at this transform margin – a seismically active boundary that separates the Pacific Plate from the North American Plate. Whereas the upper continental slope adjacent to and east (upslope) of the fault zone offshore of the Haida Gwaii is heavily gullied, few large-sized submarine landslides in this area are observed in the MBES images. However, smaller submarine seafloor slides exist locally in areas where fluid flow appears to be occurring and large seafloor slides have recently been detected at the base of the steep continental slope just above its contact with the abyssal plain on the Queen Charlotte Terrace. In addition, along the subtle slope re-entrant area offshore of the Dixon Entrance shelf bathymetric data suggest that extensive mass wasting has occurred in the vicinity of an active mud volcano venting gas. We surmise that the relative lack of submarine slides along the upper slope in close proximity to the Queen Charlotte Fault Zone may be the result of seismic strengthening (compaction and cohesion) of a sediment-starved shelf and slope through multiple seismic events.

Abstract A 6.3 m tsunami swept through Kitimat Arm, British Columbia in 1974. An even larger wave struck and damaged the Northlands Navigation dock at Kitimat and the Haisla First Nation docks at Kitamaat Village the following year. Further down the fjord, two large coastal block failures were observed on the fjord walls across from the Gitga'at village of Hartley Bay. Several large infrastructure projects have recently been proposed for the Kitimat Arm coastal areas. The Geological Survey of Canada has therefore embarked on a five-year project to understand the magnitude and frequency of submarine mass movements in this fjord system to provide information regarding the risks from these events and to propose mitigation measures that may reduce these risks. We provide here an overview and the main results to date of an ongoing multidisciplinary study, which includes palaeotsunami studies, geomorphological and sub-seabed mapping, subaerial landslide hazard assessment, tsunami modelling, in situ and laboratory geotechnical testing, and the real-time tracking of seismic activity and seafloor movement. Some of these activities are reported in greater detail elsewhere in this book. The results of this research are summarized as a list of conclusions and recommendations to the Government of Canada.