Integrated stress modelling and seismic investigation of near-surface fluid migration offshore Svalbard

Methane seepage from the seafloor at continental margins is a widespread phenomenon with potential implications for global climate and seabed ecology. How much methane is being released and which mechanisms sustain such releases over geological time remains unsolved. Organic and inorganic gas generated in the sediments migrates from depth towards the near-surface in response to hydraulic pressure changes, and eventually gets released to the oceans or the atmosphere. At continental margins, significant amounts of gas are retained in the near-surface as gas hydrates, which also act as a cap for free gas beneath the gas hydrates stability zone. Faults that are critically stressed may break this cap, thereby promoting release of trapped gas. Here, we integrate high resolution 2D and 3D seismic data and stress modelling to investigate near-surface faults and associated seepage at a deep marine gas hydrate system across the west-Svalbard margin. We study the vulnerability of the faults to 1) modeled tectonic stresses due to oblique spreading at Molloy and Knipovich mid-ocean ridges; and 2) glacially induced stresses following changes in the architecture of the Barents Sea ice-sheet since the last glacial maximum (ca. 23 ka BP). Preliminary modelling results suggest that maximum principal stresses (σ_H) from oblique spreading change orientation from NW-SE towards the Molloy Ridge to N-S/NE-SW towards the northward termination of the Knipovich ridge. Modeled glacially induced maximum horizontal stresses are generally parallel to the shelf break and vary from compressive to tensile during peak glacial to deglaciation periods. We postulate that these changes in the orientation and state of regional stresses may have promoted tensile opening in pre-existing N-S to NW-SE oriented faults, altering the pressure in the system and thus modulating the release of gas trapped at the base of the gas hydrate stability zone or at other type of shallow gas traps across west-Svalbard.