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How to Detect Water in the Mantle Wedge of a Subduction Zone Using Seismic Anisotropy
Author(s) -
Kaminski E.,
Okaya D. A.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl079571
Subject(s) - geology , mantle wedge , subduction , wedge (geometry) , mantle (geology) , trench , seismology , seismic anisotropy , anisotropy , slab , geophysics , hotspot (geology) , petrology , tectonics , geometry , optics , materials science , physics , mathematics , layer (electronics) , composite material
In approximately one fourth of worldwide subduction zones, seismic observations indicate a rotation from trench‐normal to trench‐parallel fast axis orientations in the mantle wedge. To interpret this observation we predict the evolution of crystal lattice preferred orientation in mantle wedge material as a function of the amount of water by using a model of polycrystal deformation (D‐Rex) coupled with an analytical corner flow. The resulting seismic signature is obtained from synthetic seismic wave propagation through this mantle wedge. We identify that progressive hydration produces the rotation of fast axis orientations and can generate between the two zones of trench‐parallel and trench‐normal fast axis orientations a morph zone with very small anisotropy and a related decrease in P and S wave velocities. Such a morph zone is not produced by trench‐parallel flow, hence this signature can be used to detect water in the mantle wedge.