Shear-Wave Anisotropy Above the Deflected Northwest Pacific Slab Determined using SKS and S Phases


About 700 shear-wave splitting meausurements obtained at global and regional seismic stations in NE China and Mongolia are used to infer the characteristics of mantle fabrics. The dominant fast directions (φ) at the eastern stations, which are separated from the western ones by the western boundary of a few Cenozoic sedimentary basins, are about 100° from the north, which are almost exactly the same as the motion direction of the Eurasian plate relative to the Pacific plate. Spatially varying fast diretion and splitting time (δ t) measurements are observed at stations in the western region. The boundary between the eastern and western regions approximately corresponds to the western limit of the horizontally deflected Pacific plate in the mantle transition zone. We use S-waves from deep earthquakes along the subducting slab to determine the depth of the anisotorpy region. Variation of the splitting times with focal depth suggests that the mantle tranistion zone, where the deflected slab is located, contributes the bulk of the observed splitting from SKS. The SKS and S splitting observations can be best explained by the eastward mantle flow induced by the rollback of the Japan trench.

Meeting Name

Western Pacific Geophysics Meeting (2006: Jul. 24-27, Beijing, China)


Geosciences and Geological and Petroleum Engineering

Document Type

Article - Conference proceedings

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© 2006 American Geophysical Union (AGU), All rights reserved.

Publication Date

01 Jul 2006

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