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TitreCoastal submarine failures in the Strait of Georgia, British Columbia: landslides of the 1946 Vancouver Island earthquake
AuteurMosher, D C; Monahan, P A; Barrie, J V; Courtney, R C
SourceJournal of Coastal Research vol. 20, no. 1, 2004 p. 277-291,[277:csfits];2
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 2001222
ÉditeurCoastal Education and Research Foundation
Documentpublication en série
Mediapapier; en ligne; numérique
SNRC92F/07; 92F/08; 92F/09; 92F/10; 92F/15; 92F/16
Lat/Long OENS-125.1667 -124.5000 50.0000 49.3333
Sujetsglissements de pentes; coulées boueuses; glissements de terrain; sismicité; zones sismiques; sonar latéral; levés au sonar; subduction; zones de subduction; sédiments marins; bassins; pressions interstitielles; géophysique; géologie marine; sédimentologie; Quaternaire
Illustrationslocation maps; geological sketch maps; stratigraphic columns; tables; photographs; fence diagrams; graphs
Résumé(disponible en anglais seulement)
British Columbia hosts Canada's most rapidly developing coastal communities along the semi-enclosed waterways of the Strait of Georgia. This region also is Canada's most seismically active zone. In 1946, the Vancouver Island M7.3 earthquake caused a number of submarine failures of sand and gravel shoreline deposits, destroying coastal facilities, shearing submarine cables and causing large, destructive waves. Multibeam and sidescan sonar technologies have been used to map three submarine landslides at Goose Spit, Mapleguard Spit and Grief Point. These sites are 32-55 km from the epicentre. The data image the failures in great detail, providing important information on size and style of mass-wasting. The total combined area affected by these three failures is over 1.3 3 106 m2. Submarine cores show the spit failures consisted of well-rounded beach gravel, cobble and sand, in some cases suspended in a cohesive mud matrix, while the Grief Point failure was likely a debris flow avalanche. Cone penetration tests at Goose Spit show
soil profiles prone to liquefaction, lateral spreading and post-liquefaction landsliding with reasonably low ground accelerations.