T010-0015
Computation of glacial and tectonic stress off Svalbard: implications for seabed methane seepage along the Vestnesa Ridge
Tuesday, 8 December 2020
Poster
Rémi Vachon1, Peter Schmidt2, Bjorn Lund3, Andreia Aletia Plaza-Faverola4, Stephane Beaussier5, Henry Patton6 and Alun Hubbard II6, (1)UiT The Arctic University of Norway, CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Tromsø, Norway, (2)Uppsala university, Uppsala, Sweden, (3)Uppsala University, Uppsala, Sweden, (4)UiT The Arctic University of Norway, CAGE-Centre for Arctic Gas Hydrate, Environment, and Climate, Dept. of Geology, Tromso, Norway, (5)ETH Zurich, Zurich, Switzerland, (6)CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, UiT The Arctic University of Norway, Department of Geoscience, Tromsø, Norway
Abstract:
Large amounts of methane are stored and released along continental margins. Faults and fractures play a key role in the transport of the methane toward the seabed and into the ocean. Yet, the processes that determine the pressure field that controls fault-related seepage remains poorly quantified. Here we investigate how the regional stress field (i.e., controlled by the combination of large scale tectonic processes, glacial rebound and gravitational potential energy) affects the fluid and fault dynamics off west-Svalbard. To assess the contribution of glacial stresses to the total stress field, we build a mechanical viscoelastic model underlying the area of interest. We apply an ice load at the surface of the earth model and calculate the magnitude and orientation of stress generated by glacial isostatic adjustment (GIA). The ice-sheet varies according to recent time-dependent ice-thickness models that covers Fennoscandia, Svalbard and the Barents Sea.
Our model predicts that the GIA stress contribution is compressive in regions covered by ice and tensile off the edge of the ice-sheet. The magnitude of the vertical GIA-related stress closely follows the thickness of the ice cover, whilst the horizontal stresses are governed by the isostatic adjustment. This means that the differential stress state, related to GIA, changes over the course of a glaciation which may have impact on fault stability. Along the Vestnesa Ridge, the maximum horizontal stress (σH) induced by GIA remains tensile but experience an increase in σH of about 4 MPa due to ice melting between the last glacial maximum and present time. The model does not predict a major change in the orientation of the stress vectors and σH stays constant North-South oriented along the ridge. Glacial stresses are compared with the ridge push contributions to study how temporal and spatial variations of the final stress field would affect faults in the region.
