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Shear wave splitting in the mantle Ps phases
Author(s) -
Vinnik Lev,
Montagner JeanPaul
Publication year - 1996
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 - 10.1029/96gl02263
Subject(s) - mantle (geology) , geology , anisotropy , classification of discontinuities , transition zone , shear wave splitting , core–mantle boundary , geophysics , seismic anisotropy , mantle convection , azimuth , mantle wedge , stacking , shear (geology) , seismology , petrology , physics , lithosphere , tectonics , optics , mathematical analysis , mathematics , nuclear magnetic resonance
Distribution with depth of mantle anisotropy is uncertain. To better constrain this distribution, we analyse records of the mantle Ps phases at the GRF array in Germany. Two components of these phases ( SV and T ) are detected by stacking teleseismic records of events well distributed in azimuth and distance. The detected T component signals are generated not so much by splitting of SV as by conversion from P to SH at the mantle discontinuities. To reconcile these observations with previously known observations of splitting in SKS , at least three anisotropic layers are required. The data favour a model with NNE oriented fast velocity at the top of the mantle. This is consistent with the results of other seismic studies. Beneath this layer the fast direction of anisotropy changes by around 90°. Our analysis suggests as well that a layer at the base of the mantle transition zone (MTZ) is anisotropic. This anisotropy might arise in the convective boundary layer between the upper and the lower mantle.