Global Seismology - Subduction Zones

Results from recent Nature paper. Deep events from Tonga-Fiji subduction zone recorded at Australian stations are used to study mid-mantle anisotropy in the vicinity of the slab. Large circles are colour coded averages of the estimated anisotropy magnitude.

Three models for anisotropy below the 660_km discontinuity. (a) An anisotropic mid-mantle boundary layer which may or may not be a global feature of such a boundary (b) Slab forces on the surrounding mantle lead to mid-mantle anisotropy (c) Anisotropy associated with slab material pooling in the lower mantle.

Publications

Wookey, J., J-M. Kendall and G. Barruol, 2002, Mid-mantle deformation inferred from seismic anisotropy, Nature, 415, 777-780.
Brisbourne, A., G. W. Stuart and J-M. Kendall, 1999, Anisotropic structure of the Hikurangi subduction zone, New Zealand -- Integrated interpretation of surface-wave and body-wave observations, Geophys. J. Int., 137, 214-230.
Kendall, J-M. and C. J. Thomson, 1993, Seismic modelling of subduction zones with inhomogeneity and anisotropy, I: Teleseismic P-wavefront geometry, Geophysical Journal International, 112, 39-66.