Northwest Territories Geological Survey

The formation and evolution of the lithosphere in the western Canadian Arctic represent a long-standing tectonic puzzle. The eastern Beaufort Sea margin juxtaposes young (<150 Ma) Arctic Ocean lithosphere with Paleo-Proterozoic continental lithosphere of the Canadian Shield underlying Banks Island, over <200 km. The southern Beaufort Sea Mackenzie Delta margin represents a well-developed fold and thrust belt of Cretaceous to present age, but has only been recently recognized as likely active. A concentration of poorly constrained earthquakes within the Beaufort Sea are interpreted as due to flexure of the oceanic crust in response to margin thrusting or loading of thick Mackenzie Delta sediments. We use data from new land broadband seismic networks to investigate crustal structure and seismicity around the Beaufort Sea. Preliminary results from ambient seismic noise and receiver function analyses indicate a ~30 km deep Moho beneath the Beaufort Sea and Banks Island. We examine focal depths of selected Beaufort Sea earthquakes using teleseismic P-pP times and find focal depths of ~35 km. These results suggest that earthquakes occur on reactivated passive margin structures, possibly triggered by flexural loading.