Multi‐Layer Seismic Anisotropy Beneath Greenland

Abstract

Abstract Seismic anisotropy provides insight into past episodes of lithospheric deformation and the orientations of strain in the underlying asthenosphere. The Greenland mantle has played host to a rich history of tectonic processes, including multiple orogenies and plume‐lithosphere interactions. This study presents new measurements of SKS splitting that reveal strong variations in fast polarization direction with back‐azimuth that are consistent across Greenland, including at stations where splitting measurements have not previously been reported. We compared observed fast polarization directions to the predictions of two‐layer models with olivine‐orthopyroxene anisotropy. The family of models that provides acceptable misfits at 95% confidence indicates an upper layer olivine a‐axis azimuth of 222–236°, a lower layer olivine a‐axis azimuth of 114–130°, and non‐zero a‐axis plunges. These models are consistent with an upper layer of lithospheric anisotropy due to Proterozoic and Archean orogenic fabrics, and a lower layer of anisotropy corresponding to either asthenospheric flow aligned approximately parallel to the direction of absolute plate motion and plunging due to lithospheric topography or dipping lithospheric structures created by episodes of paleo‐convergence.

Keywords

• anisotropy
• craton
• Greenland
• mantle dynamics
• shear‐wave splitting