Structure, deformation and thermal regime of the Queen Charlotte Transform Margin

This study examined thermal and neotectonic constraints on the tectonic regime of the Queen Charlotte Margin. An important application of the work is evaluating the potential for great thrust earthquakes on this primarily transform margin between the oceanic Pacific Plate to the west, and the continental North America Plate to the east. Refraction and reflection data, seismicity, gravity, bathymetry, and heat flow data were used to constrain structural and tectonic models for convergence and underthrusting along the Queen Charlotte Margin. Historical and current plate motion models indicate 20 degrees of oblique convergence along the Queen Charlotte Margin. Oblique convergence initiated between 3.0 and 8.5 Ma giving 60 to 170 km of convergence. Two end member models for the accommodation of the convergence were investigated. In the first, convergence was accommodated by deformation and shortening of the Pacific and North America Plates, with little or no underthrusting. In the second, convergence results in underthrusting of up to 170 km of oceanic crust beneath the North America Plate. The thermal data, the absence of crustal thickening (constrained by receiver function and refraction studies), and a variety of other evidence support underthrusting. (Abstract shortened by UMI.)...