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Reduced oceanic seismic anisotropy by small-scale convection

van Hunen, Jeroen; Cadek, Ondrej

Authors

Ondrej Cadek



Abstract

Amplitudes of azimuthal seismic anisotropy below the Pacific plate are observed to decrease with lithospheric age, whereas an increase is expected due to ongoing shearing between the plate and the underlying mantle. We illustrate that the convective disturbance of this laminar flow field by sub-lithospheric small-scale convection (SSC) provides an explanation for this anisotropy reduction. By combining numerical flow models with forward seismic anisotropy calculations we show that small-scale convection can disturb the anisotropy pattern significantly. When such disturbed signal is smoothed over >similar to 500 km length scale (the approximate present-day seismic resolution for azimuthal anisotropy within the Pacific lithosphere and upper mantle), our results show a significant reduction in anisotropy amplitudes of about a factor two, similar to observed reductions. Perturbations of the fast polarization direction, however, remain relatively small (

Citation

van Hunen, J., & Cadek, O. (2009). Reduced oceanic seismic anisotropy by small-scale convection. Earth and Planetary Science Letters, 284(3-4), 622-629. https://doi.org/10.1016/j.epsl.2009.05.034

Journal Article Type Article
Publication Date 2009
Journal Earth and Planetary Science Letters
Print ISSN 0012-821X
Electronic ISSN 1385-013X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 284
Issue 3-4
Pages 622-629
DOI https://doi.org/10.1016/j.epsl.2009.05.034
Keywords small-scale convection; anisotropy; oceanic lithosphere; numerical modelling
Public URL https://durham-repository.worktribe.com/output/1555463