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

Abstract

Abstract. Methane seepage occurs across the west-Svalbard margin at water depths ranging from the upper shelf 9 at < 300 m to gas hydrate systems in the deep sea at > 1000 m. The Vestnesa sedimentary ridge, located on oceanic 10 crust between 1000-1700 m water depth, hosts a perennially stable gas hydrate system with evidence of both past 11 and present-day seepage. On the ridge, an eastward transition from a zone with clear morphological evidence of 12 past seepage to a zone of active present-day seepage coincides with a change in the faulting pattern of near-surface 13 strata. We modelled the tectonic stress regime due to oblique spreading along the Molloy and Knipovich spreading 14 ridges to investigate whether spatial and temporal variations in the regional stress field may explain patterns of 15 seepage distribution. The model reveals a zone of tensile stress that extends northward from the Knipovich Ridge 16 and encompasses a zone of active seepage and extensional faulting. A zone of past seepage is presently located in 17 a strike-slip regime. Our modelling results suggest that seepage is promoted by opening of faults and fractures in 18 a tensile regime. We develop a conceptual model to describe how seepage may be controlled by an interplay 19 between tectonic stresses and pore fluid pressure within shallow gas reservoirs across the passive margin off west-20