High resolution image of the subducted Pacific (?) plate beneath central Alaska, 50-150 km depth

Publication Type  Journal Article
Year of Publication  2003
Authors  Ferris, A.; Abers, G. A.; Christensen, D. H.; Veenstra, E.
Journal Title  Earth and Planetary Science Letters
Volume  214
Issue  3-4
Pages  575-588
Journal Date  Sep 30
ISBN Number  0012-821X
Accession Number  ISI:000185550500015
Key Words  receiver function; serpentinite; yakutat; wadati-benioff zone; wave-forms; receiver functions; velocity structure; crustal thickness; northern gulf; yakutat block; oceanic-crust; body waves; constraints; mantle

A receiver function transect across the Alaska Range images the subducting Pacific plate at 50-150 km depth. Across a 200 kin long array of 30 receivers, the largest observed P-to-S conversions come from the top of the subducting slab. This signal is coherent across the array and is strongly asymmetric, requiring a complicated interface at the top of the slab. Waveform, inversion shows that the conversion is generated by a 11-22 km thick low velocity zone at the top of the slab, as much as 20% slower than the surrounding mantle. The velocity of this zone increases with increasing depth of the slab, approaching velocities of the mantle near 150 km depth. All intermediate depth earthquakes occur within the zone, along a plane dipping 5degrees steeper. The layer is too thick to represent metamorphosed oceanic crust, as proposed for other subduction zones. It may represent a thick serpentinized zone or, more likely, a thick exotic terrane subducting along with the Pacific plate. (C) 2003 Elsevier B.V. All rights reserved.


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URL  <Go to ISI>://000185550500015
DOI  Doi 10.1016/S0012-821x(03)00403-5