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TitleDo dissociating gas hydrates play a role in triggering submarine slope failures? A case study from the northern Cascadia margin
AuthorScholz, N A; Riedel, M; Spence, G D; Hyndman, R D; James, T; Naegeli, K; Dugan, B; Pohlman, J; Hamilton, T
SourceProceedings of the 7th International conference on gas hydrates (ICGH 2011); by ICGH 2011 Committee; 2011, 8 pages; 1 CD-ROM
LinksOnline - En ligne (pdf 4.36 MB)
Alt SeriesEarth Sciences Sector, Contribution Series 20110046
Meeting7th International Conference on Gas Hydrates; Edinburgh; GB; July 17-21, 2011
Mediaon-line; digital
File formatpdf
ProvinceWestern offshore region
AreaCascadia Margin; Vancouver Island; Orca Slide; Slipstream Slide
Lat/Long WENS-128.0000 -126.0000 49.0000 48.0000
Subjectstectonics; sedimentology; marine geology; geophysics; geochronology; slope failures; landslides; continental slope; slope deposits; slope stability; debris flows; debris flow deposits; gas; hydrate; seismic interpretations; cores; sea level fluctuations; sea level changes; pore pressures; shear strength; sedimentation rates; tectonic setting; radiocarbon dates; modelling; Juan de Fuca plate; Explorer plate
ProgramGas Hydrates, Gas Hydrate Characterization
AbstractSwath bathymetry from the northern Cascadia margin offshore Vancouver Island, Canada reveals several submarine landslides on the seaward slopes of the deformation frontal ridges. The slides occur in the thick accretionary prism of the subducting Juan de Fuca and Explorer plates. Possible trigger mechanisms for the slope failures include strong earthquake shaking, pore pressure changes induced by sea-level changes, and the dissociation of gas hydrates. This study focuses on two slide features of different morphology, representing the two end-members of the range of morphologies found on the margin. Orca Slide resembles a debris flow, while Slipstream Slide consists of large internally coherent sediment blocks. The presence of gas hydrates is interpreted from of a bottom simulating reflector (BSR) in regional seismic data around both slides. Near Orca Slide additional evidence for gas hydrate is available from core and logging data of Integrated Ocean Drilling Program (IODP) Expedition 311, Site U1326. We compared the timing of rapid local sealevel change with the results from radiocarbon age dating and sulfate-reduction rate modeling of previous studies on collected sediment cores to constrain the ages of the slides and potential trigger mechanisms. A link between slump-failures and gas hydrate dissociation is excess pore pressure. We determine the amount of excess pressure needed to trigger slope failure by examining sea-level changes, tectonic uplift, sedimentation rate, and sediment physical properties such as pore pressure, sediment shear strength, porosity, sediment permeability, and gas hydrate concentration. The estimation of the present state of slope stability, the reconstruction of the slide dynamics and of the subsequent forces on the overlying water column have the potential to contribute to the assessment of local tsunami hazard.