Shun-Ichiro Karato

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Several hypotheses have been proposed to explain trench-parallel shear wave splitting in the mantle wedge of subduction zones. These include 3-D flow effects, parallel melt filled cracks, and B-type olivine fabric. We predict the distribution of B-type and other fabrics with high-resolution thermal and stress models of subduction zones. A composite viscous(More)
Because of their distinct chemical signatures, ocean-island and mid-ocean-ridge basalts are traditionally inferred to arise from separate, isolated reservoirs in the Earth's mantle. Such mantle reservoir models, however, typically satisfy geochemical constraints, but not geophysical observations. Here we propose an alternative hypothesis that, rather than(More)
The distribution of water in the Earth's interior reflects the way in which the Earth has evolved, and has an important influence on its material properties. Minerals in the transition zone of the Earth's mantle (from approximately 410 to approximately 660 km depth) have large water solubility, and hence it is thought that the transition zone might act as a(More)
Seismological observations reveal highly anisotropic patches at the bottom of the Earth's lower mantle, whereas the bulk of the mantle has been observed to be largely isotropic. These patches have been interpreted to correspond to areas where subduction has taken place in the past or to areas where mantle plumes are upwelling, but the underlying cause for(More)
[1] Seismological observations have revealed patches of seismic anisotropy in regions related to mantle upwelling and paleosubduction within an otherwise isotropic lower mantle. A combination of numerical modeling and mineral physics is used to constrain the source of anisotropy in these regions in an effort to better understand lower mantle dynamics and(More)
[1] Many characteristics of D 00 layer may be attributed to the recently discovered MgSiO 3 post-perovskite phase without chemical heterogeneities. They include a sharp discontinuity at the top of D 00 , regional variation in seismic anisotropy, and a steep Clapeyron slope. However, some features remain unexplained. The seismically inferred velocity jump is(More)
Water, the most abundant volatile in Earth's interior, preserves the young surface of our planet by catalysing mantle convection, lubricating plate tectonics and feeding arc volcanism. Since planetary accretion, water has been exchanged between the hydrosphere and the geosphere, but its depth distribution in the mantle remains elusive. Water drastically(More)
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