Tsunami hazard from submarine landslides on the Oregon continental slope

The morphometric analysis of submarine landslides on the continental slope of Oregon provides insight into tsunami hazard, including the locations of mass movements, the sizes of mass failures, their relative importance to the structure of a given margin, and the potential for landslide-generated tsunami hazards. Numerous, often overlapping failures, including two super-scale slumps in the southern Oregon margin, may have had the capacity to produce very large tsunamis, and should be considered when assessing earthquake and tsunami hazard in the Cascadia Subduction Zone. We use various aspects of the slides, including the mean water depth, width, run-out distance, and thickness, along with the slope gradient in the scar and adjacent slopes (and radius of curvature of the failure plane for slumps) to predict maximum tsunami amplitudes directly above the failure. Cohesive landslides tend to have higher headscarps than the slides that lose cohesion, suggesting that they occur in stronger sediment, and have the potential to produce larger tsunamis. On other continental margins (California, Texas/Louisiana, and New Jersey/Maryland), landslides tend to occur on slopes less than 4°, however offshore Oregon, most of the landslides occur on slopes over 15°; the failures on the steeper slopes tend to produce larger tsunamis. There are surprisingly few large failures along the seismically active northern margin, implying that strong shaking maybe limited in this region, and tsunami generation may be due to coincident movement along faults on the upper plate.