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| Titel |
Effect of seismic anisotropy on P tomography images of the Baltic Shield. |
| VerfasserIn |
T. Eken, J. Plomerova, R. Roberts, L. Vecsey, H. Shomali, V. Babuska, R. Bodvarsson |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020246
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| Zusammenfassung |
| It has been previously suggested that ignoring seismic anisotropy can distort tomographic
images. We investigate possible effects of neglecting seismic anisotropy on P-velocity
tomographic images of the Baltic Shield. Isotropic inversions of teleseismic P- and
S-wave data (Eken et al, 2007; 2008) indicated a slab-like structure between 65 and
68N, continuing to a depth of around 350-450 km and dipping gently towards
the north. A joint inversion/interpretation of body-wave anisotropic parameters
(shear-wave splitting and P-residual spheres (Eken et al., Tectonophysics, submitted)
showed that the upper mantle and particularly the mantle lithosphere is anisotropic. A
synthetic test performed with real ray geometry of observed data and based on 3D
self-consistent anisotropic models retrieved by the joint inversion of body-wave
parameters, show effects in tomography images caused by neglecting anisotropy.
We also calculated an isotropic inversion from data “corrected for anisotropy”.
Constituents corresponding to anisotropic propagation were evaluated (1) from
directional terms of relative P residuals and (2) from the 3D self-consistent models.
The inversion is calculated from 4200 observed P travel-time residuals from 136
teleseismic earthquakes. The general pattern of the velocity-perturbation images does not
change. The slab-like structure identified in the pure isotropic inversion appears in
the new inversion with lower amplitude. Velocity-perturbations below about 250
km decrease in whole the model, which is about the lithosphere thickness of the
Baltic Shield, with which we associate the laterally variable seismic anisotropy. The
maximum difference in estimated velocity perturbations between the two inversions is
about 1%, with a total range of about |
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