Back to Search
Start Over
Olivine fabric transitions and shear wave anisotropy in the Ryukyu subduction system
- Source :
-
Earth & Planetary Science Letters . Apr2008, Vol. 268 Issue 3/4, p268-282. 15p. - Publication Year :
- 2008
-
Abstract
- Abstract: Recent shear wave splitting measurements from the fore-arc region of the Ryukyu subduction system show large magnitude (0.3–1.6 s) trench-parallel splitting in both local and teleseismic phases. The similarity of splitting parameters associated with shallow local-S and teleseismic phases suggests that the source of anisotropy is located in the fore-arc mantle. One explanation for this pattern of shear wave splitting involves a transition from commonly observed high-temperature olivine fabrics with flow-parallel seismically fast directions to a flow-normal B-type olivine fabric in the cold fore-arc mantle of the Ryukyu wedge. We test the B-type fabric hypothesis by comparing observed splitting parameters to those predicted from geodynamic models that incorporate olivine fabric development. The distribution of olivine fabric is calculated with high-resolution thermomechanical models of the Ryukyu subduction zone that include realistic slab geometry and an experimentally based wet olivine rheology. We conclude that B-type fabric can explain the magnitude and trench-parallel orientation of deep local-S phases that sample the core of the fore-arc mantle. However, our calculations show that B-type fabric alone cannot account for large magnitude trench-parallel splitting associated with teleseismic phases that sample the shallow tip of the fore-arc mantle. Alternative models for trench-parallel teleseismic splitting in the shallow tip of the fore-arc mantle involve the addition of crustal or slab anisotropy and highly anisotropic foliated antigorite serpentinite. [Copyright &y& Elsevier]
- Subjects :
- *ROCK-forming minerals
*PROPERTIES of matter
*SUBDUCTION zones
*PLATE tectonics
Subjects
Details
- Language :
- English
- ISSN :
- 0012821X
- Volume :
- 268
- Issue :
- 3/4
- Database :
- Academic Search Index
- Journal :
- Earth & Planetary Science Letters
- Publication Type :
- Academic Journal
- Accession number :
- 31561103
- Full Text :
- https://doi.org/10.1016/j.epsl.2008.01.004