Submarine landslides offshore Vancouver Island along the northern Cascadia margin, British Columbia: why preconditioning is likely required to trigger slope failure.

Scholz, Nastasja A., Riedel, Michael , Urlaub, Morelia , Spence, George D. and Hyndman, Roy D. (2016) Submarine landslides offshore Vancouver Island along the northern Cascadia margin, British Columbia: why preconditioning is likely required to trigger slope failure. Geo-Marine Letters, 36 (5). pp. 323-337. DOI 10.1007/s00367-016-0452-8.

[img] Text
Scholz.pdf - Published Version
Restricted to Registered users only

Download (7Mb) | Contact
[img] Text
367_2016_452_MOESM1_ESM.pdf - Supplemental Material
Restricted to Registered users only

Download (337Kb) | Contact

Supplementary data:

Abstract

Bathymetric data reveal abundant submarine landslides along the deformation front of the northern Cascadia margin that might have significant tsunami potential. Radiocarbon age dating showed that slope failures are early to mid-Holocene. The aim of this study is the analysis of slope stability to investigate possible trigger mechanisms using the factor of safety analysis technique on two prominent frontal ridges. First-order values for the earthquake shaking required to generate instability are derived. These are compared to estimated ground accelerations for large (M=5 to 8) crustal earthquakes to giant (M=8 to 9) megathrust events. The results suggest that estimated earthquake accelerations are insufficient to destabilize the slopes, unless the normal sediment frictional resistance is significantly reduced by, for example, excess pore pressure. Elevated pore pressure (overpressure ratio of 0.4) should significantly lower the threshold for earthquake shaking, so that a medium-sized M=5 earthquake at 10 km distance may trigger submarine landslides. Preconditioning of the slopes must be limited primarily to the mid- to early Holocene as slope failures are constrained to this period. The most likely causes for excess pore pressures include rapid sedimentation at the time of glacial retreat, sediment tectonic deformation, and gas hydrate dissociation as result of ocean warming and sea level rise. No slope failures comparable in size and volume have occurred since that time. Megathrust earthquakes have occurred frequently since the most recent failures in the mid-Holocene, which emphasizes the importance of preconditioning for submarine slope stability.

Document Type: Article
Additional Information: WOS:000383468800001
Keywords: Submarine landslides, Vancouver Island, northern Cascadia margin
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1007/s00367-016-0452-8
ISSN: 0276-0460
Date Deposited: 20 May 2016 09:42
Last Modified: 01 Feb 2019 15:04
URI: http://oceanrep.geomar.de/id/eprint/32898

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...