Lateral Variations in Compressional/Shear Velocities at the Base of the Mantle
- 2 April 1999
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 284 (5411) , 120-125
- https://doi.org/10.1126/science.284.5411.120
Abstract
Observations of core-diffracted P(P diff) and SH(SH diff) waves recorded by the Missouri-to-Massachusetts (MOMA) seismic array show that the ratio of compressional (P) seismic velocities to horizontal shear (SH) velocities at the base of the mantle changes abruptly from beneath the mid-Pacific (VP /VS = 1.88, also the value predicted by reference Earth models) to beneath Alaska (VP /VS = 1.83). This change signifies a sudden lateral variation in material properties that may have a mineralogical or textural origin. A textural change could be a result of shear stresses induced during the arrival at the core of ancient lithosphere from the northern Pacific paleotrench.Keywords
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