Lehmann discontinuity beneath North America: No role for seismic anisotropy | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Lehmann discontinuity beneath North America: No role for seismic anisotropy

Type de publication:

Journal Article

Source:

Geophysical Research Letters, Volume 32, Ticket 9, p.L09306, doi:10.10129/2004GL022333 (2005)

ISBN:

0094-8276

URL:

http://www.agu.org/

Mots-clés:

Sismologie ; MODELISATION ; S-RECEIVER FUNCTIONS; UPPER-MANTLE; CONTINENTS; THICKNESS; LAYER, UMR 7154

Résumé:

The Lehmann discontinuity in the upper mantle is often interpreted as a boundary separating anisotropic and isotropic media. We demonstrate, however, that seismic anisotropy plays, if any, a minor role in the origin of the Lehmann discontinuity. Our data are obtained with S receiver function technique from recordings of the MOMA seismograph array in the eastern USA. Part of the data is processed with a new modification of this technique. We observe Sp phase converted from the Lehmann discontinuity at a depth around 200 km with comparable amplitudes and similar polarities in two azimuths differing by about 90 degrees. Contrary to the observations, the polarity in the synthetic seismograms for models with azimuthal anisotropy is opposite for the azimuths differing by 90 degrees. Radial anisotropy with a slow vertical direction results in the Sp phase with the polarity opposite to the observed one.

Notes:

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