| The Steen River impact crater, Alberta, is buried under ∼200 m of Cretaceous rocks requiring geophysical/drilling projects for its exploration. Comparison of radial and concentric 2D refraction velocity models, constrained by drillhole information and crossing at the crater's rim, suggest the presence of different anisotropy directions at different stratigraphic levels. A 3D refraction velocity model indicates non-homogeneous and azimuthally anisotropic velocity distributions at the rim. High resolution 2D interval velocity models, guided by the seismically defined sub-surface deformation, reveal a two-stage history of impact-induced compressional deformation followed by extension. Combined interpretation of refraction and interval velocity models suggest the coexistence at the rim of impact-induced azimuthal velocity anisotropy below the Cretaceous unconformity, and folding/faulting-induced azimuthal velocity anisotropy below the Slave Point Formation. 2-component rotation analysis of converted wave data indicates that the Cretaceous rocks at Steen River are also anisotropic. |
