Publication Date:
2004-01-17
Description:
We applied global waveform tomography to model radial anisotropy in the whole mantle. We found that in the last few hundred kilometers near the core-mantle boundary, horizontally polarized S-wave velocities (VSH) are, on average, faster (by approximately 1%) than vertically polarized S-wave velocities (VSV), suggesting a large-scale predominance of horizontal shear. This confirms that the D" region at the base of the mantle is also a mechanical boundary layer for mantle convection. A notable exception to this average signature can be found at the base of the two broad low-velocity regions under the Pacific Ocean and under Africa, often referred to as "superplumes," where the anisotropic pattern indicates the onset of vertical flow.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Panning, Mark -- Romanowicz, Barbara -- New York, N.Y. -- Science. 2004 Jan 16;303(5656):351-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Berkeley Seismological Laboratory, 215 McCone Hall, University of California, Berkeley, CA 94720, USA. mpanning@seismo.berkeley.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14726586" target="_blank"〉PubMed〈/a〉
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
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Chemistry and Pharmacology
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Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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