Seismic evidence for a weakened thick crust at the Beaufort Sea
continental margin
Abstract
The 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 a subduction initiation process.