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Anticorrelated seismic velocity anomalies from post-perovskite in the lowermost mantle

Science

By:
, , , and
DOI: 10.1126/science.1155822

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Abstract

Earth's lowermost mantle has thermal, chemical, and mineralogical complexities that require precise seismological characterization. Stacking, migration, and modeling of over 10,000 P and S waves that traverse the deep mantle under the Cocos plate resolve structures above the core-mantle boundary. A small -0.07 ?? 0.15% decrease of P wave velocity (Vp) is accompanied by a 1.5 ?? 0.5% increase in S wave velocity (Vs) near a depth of 2570 km. Bulk-sound velocity [Vb = (V p2 - 4/3Vs2)1/2] decreases by -1.0 ?? 0.5% at this depth. Transition of the primary lower-mantle mineral, (Mg1-x-y FexAly)(Si,Al) O3 perovskite, to denser post-perovskite is expected to have a negligible effect on the bulk modulus while increasing the shear modulus by ???6%, resulting in local anticorrelation of Vb and Vs anomalies; this behavior explains the data well.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Anticorrelated seismic velocity anomalies from post-perovskite in the lowermost mantle
Series title:
Science
DOI:
10.1126/science.1155822
Volume
320
Issue:
5879
Year Published:
2008
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Science
First page:
1070
Last page:
1074