Author's personal copy Discussion

We thank Tommasi and Mainprice (2008) for their interest in our work, the purpose of which was to present new seismological constraints on mantle anisotropy. Our interpretation, a few sentences in the whole manuscript, was intentionally kept short and vague and was only meant as a possible explanation. We agree that it is oversimplified and welcome their three comments which provide additional possibilities. Point 1: We stated that the absence of significant anisotropy in the lower mantle was likely to be due to a regime of diffusion creep. We were not aware of the work of Mainprice et al. (2008) on perovskite which was published after our paper. We acknowledge that preferred orientation in polycrystals may develop with modest overall anisotropy consistent with our results. Point 2: We adopted the simple view that a change of sign of anisotropy in the uppermost mantle indicates a change in the flo