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Thermal structure, radial anisotropy, and dynamics of oceanic boundary layers
Author(s) -
Auer Ludwig,
Becker Thorsten W.,
Boschi Lapo,
Schmerr Nicholas
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066246
Subject(s) - geology , lithosphere , anisotropy , seismic anisotropy , geophysics , isotropy , classification of discontinuities , seismology , mantle (geology) , geometry , tectonics , physics , optics , mathematical analysis , mathematics
Defining the oceanic lithosphere as a thermal boundary layer allows to explain, to first order, age‐dependent bathymetry and isotropic wave speeds. In contrast, SS precursors and receiver functions suggest a subhorizontal interface within this layer, on top of a radially anisotropic zone. Comparing a suite of geodynamic scenarios against surface wave dispersion data and seismic discontinuities, we find that only weak age dependency of the radially anisotropic zone is compatible with observations. We show that this zone is confined from below by a second weaker seismic interface. While observed azimuthal anisotropy is consistent with lattice‐preferred orientation of olivine due to asthenospheric flow underneath the lithosphere, radial anisotropy requires additional contributions, perhaps from petrological fabrics or melt ponding. This implies that seismic reflectors previously associated with the base of the lithosphere are instead associated with preserved structures embedded in it. They carry information about plate formation but have little control on plate deformation.