Seismic Evidence for a Weakened Thick Crust at the Beaufort Sea Continental Margin

Abstract

AbstractThe Canadian Beaufort Sea continental margin of northwestern Canada is a Cenozoic convergent margin, potentially representing a rare case of incipient subduction. Here, we produce P‐ and S‐wave seismic velocity models of the crust and the uppermost mantle using recordings from regional earthquakes. Our models reveal a northwest‐dipping very low‐velocity anomaly within the crust (δV up to −15%) beneath the Romanzof Uplift. We interpret this low‐velocity feature to correspond to a weaker and thicker crust due to shortening and stacking of igneous and sedimentary rocks. The co‐location of the thickened crust and lack of present‐day seismicity indicates that north‐south compression is accommodated by slow, aseismic deformation in the narrow margin beneath the Romanzof Uplift or more broadly offshore. Neither interpretation requires nor precludes a subduction initiation process.