This dissertation investigates the nature of submarine landslides along the deformation front of the northern Cascadia subduction zone. As the first slope stability analysis on the west coast of Vancouver Island, this study covers a variety of large-scale tectonic to small-scale, site-specific factors to investigate the nature of slope failure. Slope failure occurred mainly on the steep slopes of frontal ridges that were formed by compressive forces due to the subduction of the Juan de Fuca plate. Multi-beam swath bathymetry data are used to study the morphology of the whole margin and the geometry of two Holocene landslides that serve as representative examples. The overall margin stability is estimated using the critical taper theory, and a first-order limit equilibrium slope stability analysis provides threshold values for external forces to cause slope failure. The present-day pore pressure regime at different sites of the Cascadia margin is estimated from log-density data and expected ground accelerations are calculated via ground motion attenuation relationships. A comparison to threshold values derived from the limit equilibrium analysis suggests that, at present, slope stability is more sensitive to overpressure than to earthquake shaking. Differences in power spectral density derived from OBS-velocity data imply a slightly amplified ground response at the ridge crest compared to sites along the continental shelf and abyssal plain. Apart from estimating the trigger mechanisms of submarine landslides offshore Vancouver Island, a particular consideration is given to the potential link between slope failure and methane hydrate occurrence. The history of the gas hydrate stability zone (GHSZ) boundaries is investigated using information on regional sea-level history. Assuming colder ocean-bottom temperatures during the Holocene, a gradual shoaling of the BSR is inferred, which potentially could have caused hydrate melting. Pore pressure due to hydrate dissociation, as estimated by a previously developed method, varies over several orders of magnitude. Depending on sediment permeability, overpressure ratios can be comparable to threshold values. The two Holocene landslides are modeled numerically using a two-dimensional finite difference code in order to recreate the along-strike variability in ridge geometry and slide morphology observed along the northern Cascadia margin. Geometry and morphology correlate with the two prevalent slide mechanisms and model results suggest that sediment yield strength and average slide thickness are associated with the slide mechanism as well. / Graduate / 0373 / nscholz@uvic.ca

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Thesis (Ph. D. - Geosciences)--University of Arizona. / Part of folded illustrative matter in pocket. Includes bibliographical references.

Thesis (Ph. D.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 16, 2008). Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains x, 106 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 92-93).

Thesis (M.Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 150-157) Also available in print.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains vi, 45 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 41-43).

Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 127-133).

Thesis (Ph. D.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 134-143).

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 150-157).