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TitreRupture area and displacement of past Cascadia great earthquakes from coastal coseismic subsidence
AuteurLeonard, L J; Currie, C A; Mazzotti, S; Hyndman, R D
SourceGeological Society of America Bulletin vol. 122, no. 11/12, 2010 p. 2079-2096,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20090311
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'ouest
Lat/Long OENS-132.0000 -122.0000 52.0000 40.0000
Sujetssecousses séismiques; études séismiques; magnitudes des séismes; sismicité; zones sismiques; risque sismique; déplacement; subduction; zones de subduction; tectonique de plaques; antécédents tectoniques; milieux tectoniques; interprétations tectoniques; cadre tectonique; Zone de subduction de Cascadia ; Plaque de Juan de Fuca; géophysique; tectonique
Illustrationslocation maps; block diagrams; plots; tables
ProgrammeNational-Scale Geohazard Assessments, Géoscience pour la sécurité publique
Diffusé2010 09 01
Résumé(disponible en anglais seulement)
Coastal marshes record a 6500 yr history of coseismic displacements in great earthquakes at the Cascadia subduction zone. We compiled estimates of coseismic displacement for past megathrust events based on correlations with megathrust-triggered turbidites, and estimated megathrust slip based on comparisons of marsh displacements with dislocation model predictions. Age-correlated marsh data are compatible with event rupture extents defi ned by the published turbidite record , and a 6500 yr mean recurrence interval that increases northward from ~230 to ~480 yr. Within the constraints of the marsh data, the width of the coseismic rupture zone generally agrees with the downdip width of the interseismic locked zone inferred from geodetic and thermal data. In southernmost Cascadia, where the model does not include the complex deformation near the Mendocino triple junction, the coastal data may be better fi t by a model with an ~25% narrower rupture than that inferred from regional geophysical data. At each coastal marsh site, coseismic displacements are roughly similar from event to event, independent of the time since the previous event. Slip in the A.D. 1700 earthquake was consistent with the preceding interval of strain accumulation (~200 yr) only at the northern and southern ends of the margin, but it was apparently much higher in southern Washington and northern Oregon, possibly indicating postseismic contamination and/or catch-up coseismic slip to make up for a defi cit in the preceding event. Overall agreement between the dislocation models and the marsh data for most of the margin implies that such models can be usefully applied to rupture and ground shaking predictions.