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Discussion papers | Copyright
https://doi.org/10.5194/se-2018-11
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 18 Apr 2018

Research article | 18 Apr 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Solid Earth (SE).

Correlation between tectonic stress regimes and methane seepage on the west-Svalbard margin

Andreia Plaza-Faverola1 and Marie Keiding2 Andreia Plaza-Faverola and Marie Keiding
  • 1CAGE-Centre for Arctic Gas Hydrate, Environment, and Climate; Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
  • 2Geological Survey of Norway (NGU), P.O. Box 6315 Torgarden, 7491 Trondheim, Norway

Abstract. Methane seepage occurs across the west-Svalbard margin at water depths ranging from the upper shelf at <300m to gas hydrate systems in the deep sea at >1000m. The Vestnesa sedimentary ridge, located on oceanic crust between 1000–1700m water depth, hosts a perennially stable gas hydrate system with evidence of both past and present-day seepage. On the ridge, an eastward transition from a zone with clear morphological evidence of past seepage to a zone of active present-day seepage coincides with a change in the faulting pattern of near-surface strata. We modelled the tectonic stress regime due to oblique spreading along the Molloy and Knipovich spreading ridges to investigate whether spatial and temporal variations in the regional stress field may explain patterns of seepage distribution. The model reveals a zone of tensile stress that extends northward from the Knipovich Ridge and encompasses a zone of active seepage and extensional faulting. A zone of past seepage is presently located in a strike-slip regime. Our modelling results suggest that seepage is promoted by opening of faults and fractures in a tensile regime. We develop a conceptual model to describe how seepage may be controlled by an interplay between tectonic stresses and pore fluid pressure within shallow gas reservoirs across the passive margin off west-Svalbard. Glacio-isostatic flexural stresses may have influenced fluid dynamics along the Vestnesa Ridge in the past, explaining the presence of dormant pockmarks outside the ridge segment that is under a tensile regime at present and reconciling formerly suggested models of seepage periodicity linked to glacial cycles.

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Andreia Plaza-Faverola and Marie Keiding
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Andreia Plaza-Faverola and Marie Keiding
Andreia Plaza-Faverola and Marie Keiding
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Latest update: 19 Sep 2018
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Short summary
Vast amounts of methane are released from marine sediments at continental margins (seepage). The mechanisms controlling when and how much methane is released are not fully understood. Offshore west-Svalbard zones of active seepage are adjacent to zones of past seepage. We modelled the stress generated on the sediments exclusively due to the opening of the mid-ocean ridges in the Fram Strait and found that changes in the stress field may be controlling where and when does seepage occur.
Vast amounts of methane are released from marine sediments at continental margins (seepage). The...
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