Shoberg, T., and C. R. Bina, Some effects of remanent anisotropy on velocity contrasts between subducting lithosphere and overriding mantle at convergent margins, Geophysical Research Letters, 21, 1951-1954, 1994.
Abstract. Studies of converted seismic phases at slab-mantle boundaries indicate faster velocities in the subducting slab than in the overlying mantle. We compute theoretical contributions to velocity anisotropy from preferred crystal alignment due to finite strain for three mantle flow models which, when juxtaposed with the predicted anisotropy in the subducted lithosphere, gives rise to a velocity contrast that, necglecting all other effects, we can compare with those observed. We find a strong dip dependence in the predicted velocity anisotropy due to alignment of the slow axis in the over-riding mantle perpendicular to the slab-mantle interface. Moreover, we find it difficult to produce greater velocity in the subducting slab than in the overlying mantle for near vertical propagation paths in two of the three mantle flow models (flow parallel to the convergence direction and isotropic) at high strain rates. We do, however, predict such contrasts using a model invoking dip-axis-parallel mantle flow. Calculations for the Japan Trench subduction zone predict velocity contrasts from all three models that are too small to explain those observed from typical ScSp studies.Copyright © 1994 American Geophysical Union