TY - JOUR
T1 - Anticorrelated seismic velocity anomalies from post-perovskite in the lowermost mantle
AU - Hutko, Alexander R.
AU - Lay, Thorne
AU - Revenaugh, Justin
AU - Garnero, Edward J.
PY - 2008/5/23
Y1 - 2008/5/23
N2 - 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.
AB - 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.
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U2 - 10.1126/science.1155822
DO - 10.1126/science.1155822
M3 - Article
C2 - 18497297
AN - SCOPUS:46449106002
SN - 0036-8075
VL - 320
SP - 1070
EP - 1074
JO - Science
JF - Science
IS - 5879
ER -