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TitreSeafloor compliance imaging of marine gas hydrate deposits and cold vent structures
AuteurWilloughby, E C; Latychev, K; Edwards, R N; Schwalenberg, K; Hyndman, R D
SourceJournal of Geophysical Research vol. 113, B07107, 2008, 10 pages, (Accès ouvert)
Séries alt.Secteur des sciences de la Terre, Contribution externe 2005522
Séries alt.Secteur des sciences de la Terre, Contribution externe 20080458
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'ouest
Lat/Long OENS-127.0000 -126.5000 48.7167 48.6500
Sujetstopographie du fond océanique; topographie du fond océanique; events hydrothermaux sous-marins; levés sismiques; levés sismiques marins; levés de reflexion sismiques; études de réflexion; hydrate; hydrocarbures; déformation; géologie marine; géophysique; combustibles fossiles
Illustrationslocation maps; models; seismic profiles; plots
ProgrammeLes hydrates de gaz - carburant de l'avenir?
Diffusé2008 07 24
Résumé(disponible en anglais seulement)
Seafloor compliance, the transfer function between pressure induced by surface gravity waves and the associated seafloor deformation, can address outstanding questions about the nature of seismic blank zones, identified as cold vents offshore Vancouver Island, near Ocean Drilling Program (ODP) Site 889 and the recent Integrated Ocean Drilling Program (IODP) Expedition 311. Despite extensive seismic studies, it is not known whether free gas or gas hydrate is primarily responsible for the seismic blanking, nor are the concentration and distribution of either component conclusively determined. Here we use the formation's shear modulus to distinguish between gas hydrate, which can strongly alter the shear modulus, and free gas, which cannot. The depth-dependent gas hydrate distribution and pore-space saturation are estimated from the frequency variation of seafloor compliance measurements sensitive to the formation's shear modulus. Compliance data are consistent with pervasive moderate hydrate concentration over a broad region and significantly higher cylindrical concentrations associated with the cold vents, perhaps as much as 9 × 106 m3 in the 400 m diameter Bullseye vent, in agreement with controlled-source electromagnetic data. Compliance data can help distinguish between different models for the structure of such gas hydrate-bearing cold vents.