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

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 59-66). Also available on the World Wide Web.

Thesis (Ph. D.)--Columbia University, 1973. / Includes bibliographical references (leaves 522-541).

Thesis (M.S.)--University of California, Santa Cruz, 1988. / Typescript. Includes bibliographical references (leaves 60-65).

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2010. / Thesis Advisor(s): Rice, Joseph A. "June 2010." Description based on title screen as viewed on July 14, 2010. Author(s) subject terms: underwater acoustics, Seaweb, Deep Seaweb, undersea noise calculation, ocean trenches, surveillance, anti-submarine warfare, maritime domain awareness, passive detection, reliable acoustic path, sensor network Includes bibliographical references (p. 47-48). Also available in print.

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Approved for public release; distribution is unlimited / The purpose of this thesis is to assess the benefit of assimilating satellite altimeter data into the Modular Ocean Data Assimilation System (MODAS). To accomplish this, two different MODAS fields were used by the Weapon Acoustic Preset Program (WAPP) to determine suggested presets for a Mk 48 variant torpedo. The MODAS fields differ in that one uses altimeter data assimilated from three satellites while the other uses no altimeter data. The metric used to compare the two sets of outputs is the relative difference in acoustic coverage area generated by WAPP. Output presets are created for five different scenarios, two Anti- Surface Warfare scenarios and three Anti-Submarine Warfare scenarios, in each of three regions: the East China Sea, the Sea of Japan, and an area south of Japan that includes the Kuroshio current. Analysis of the output reveals that, in some situations, WAPP output is very sensitive to the inclusion of the altimeter data because of the resulting differences in the subsurface predictions. The change in weapon presets could be so much that the effectiveness of the weapon might be affected. / Lieutenant Commander, United States Navy

The purpose of this project is to investigate the feasibility of and methodology for the development of a set of environmental analogs of operational Undersea Warfare (USW) areas within fleet training areas. It is primarily a discussion of the identification of parameters that characterize the tactical USW environment, prioritization of these parameters, identification of existing databases that contain these parameters and an outline of the processes required to extract the desired data from the databases. An example of two operational areas with probable analogous training areas is discussed in terms of the methodology proposed. Among the environmental parameters considered are: bathymetry, sediment type, sound velocity profiles, acoustic response of the environment across a broad frequency spectrum (for both active and passive sonar), ambient noise, shipping density, bioluminescent properties, evaporation duct height, atmospheric surface duct height and gravitational anomalies. The project focus is primarily on acoustic oceanographic features but non-acoustic and atmospheric features are considered. There is an expectation that this project is the starting point for further research, software product development, data extraction, analog identification and promulgation of a tailored product to the fleet. The ultimate goal is to train for USW across the fleet in areas as much like the areas the Navy fights in as possible.