Neotectonics and seismicity in the south-eastern Beaufort Sea, polar continental margin of north-western Canada

A two-dimensional numerical model is presented that links inferences about recent rates of onshore uplift in the area of the Mackenzie Delta to rapid subsidence of the offshore Beaufort-Mackenzie Basin and the present-day upper lithospheric structure across the continent-ocean transition in this region of north-western Canada. The model results comprise a self-consistent set of internal displacements (velocities) and boundary conditions which predict a concentration of shear stress in the oceanic crust (and overlying sedimentary basin) in a region of the south-eastern Beaufort Sea featuring a concentration of earthquake epicentres. The mode of faulting implied by the calculated stress tensors is normal, consistent with a published fault-plane solution and in-situ stress measurements suggesting the axis of maximum compression to be perpendicular to the model cross-section. The results indicate that the uplift/subsidence pattern and seismicity are tectonically related but do not support models invoking tectonic compression, which have been previously proposed here and on other seismically active continental margins with rapidly subsiding sedimentary basins. Rather, a key role for dynamic processes in the upper mantle (including the asthenosphere), related to the continent-ocean lithosphere transition at passive continental margins, is implied. (C) 1998 Elsevier Science Ltd. All rights reserved.