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Detailed Reference Information |
Avants, M., Lay, T. and Garnero, E.J. (2006). A new probe of ULVZ S-wave velocity structure: Array stacking of ScS waveforms. Geophysical Research Letters 33: doi: 10.1029/2005GL024989. issn: 0094-8276. |
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S-wave velocity reductions in thin layers above the core-mantle boundary (CMB) are resolved by modeling precursors to the tangential-components of core-reflected ScS phases. Unlike most phases used to study ultra-low velocity zone (ULVZ) structure, ScS provides direct sensitivity to shear velocity structure, VS. Recordings of deep earthquakes in the Tonga-Fiji and South American subduction zones at broadband seismic networks in western North America are used to map small-scale ULVZ variability. A two-layer low-VS structure exists under the central Pacific: an abrupt 0.8--2.0% decrease 60--86 km above the CMB is underlain by a 24--30 km thick ULVZ layer having reductions of 3.3--7.4% (with respect to PREM). No corresponding velocity reductions are found under the Cocos plate. The structure above the ULVZ may be associated with reverse transformation of post-perovskite to perovskite in a steep thermal gradient in a boundary layer above the CMB. |
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Abstract |
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Keywords
Seismology, Body waves, Seismology, Seismology, Core (1212, 1213, 8124), Seismology, Mantle (1212, 1213, 8124), Tectonophysics, Earth's interior, composition and state (1212, 7207, 7208, 8105) |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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