iPlex Lunch winter-2013

The mantle transition zone (MTZ) is defined by discontinuities in seismic wave velocities at 410 km and 670 km depth that mostly result from phase changes in the olivine structure. Because the MTZ is believed to play an important role in the thermochemical evolution of our planet, constraining mantle flow at these depths is important for our understanding of mantle dynamics and the history of plate tectonics. Seismic anisotropy can help us in that regard since it can result from deformation by dislocation creep during convection and provides the most direct constraints on mantle flow patterns. Here we used a recent seismic dataset with much higher depth resolution than in previous work to constrain the three-dimensional pattern of seismic anisotropy in the top 1000 km of the mantle, and in particular in the MTZ. In this talk I will present our 3-D anisotropy model, how it was obtained, and describe how our new inferences on anisotropy can provide constraints on the deformation mechanisms taking place in the mantle