Seismic anisotropy and geodynamics of the East Japan subduction zone

Zhao, Dapeng; Wang, Jian; Huang, Zhouchuan; Liu, Xin; Wang, Zewei

doi:10.1016/j.jog.2023.101975

Cited by 5 publications

(1 citation statement)

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“…Seismic anisotropy is one of the most powerful tools to detect mantle flow and lithospheric deformation because deformation yields lattice‐preferred orientation of anisotropic minerals or shape‐preferred orientation of isotropic minerals (Ismaı̈l & Mainprice, 1998; Karato et al., 2008). In the past decades, shear‐wave splitting (SWS) measurements have provided abundant information on seismic anisotropy in subduction zones (e.g., Bodmer et al., 2015; Currie et al., 2004; Eakin et al., 2010; Long, 2016; Martin‐Short et al., 2015; Zhao, Wang, et al., 2023). When penetrating an anisotropic medium, a shear wave splits into fast and slow polarized waves in orthogonal directions, and the fast wave through the subslab mantle exhibits a predominantly trench‐parallel direction globally (Figure 1a) (Long, 2013).…”

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confidence: 99%

Mapping Mantle Flows and Slab Anisotropy in the Cascadia Subduction Zone

Liang,

Zhao,

Hua

et al. 2023

Geophysical Research Letters

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The Cascadia margin is an unusual subduction zone characterized by the downdip movement of young and thin oceanic plates, where mantle flow and intraslab deformation are still unclear. Here we present new anisotropic tomography of the Cascadia subduction zone, in which the hexagonal symmetry axis of anisotropy is tilting rather than horizontal or vertical as assumed in previous studies of seismic anisotropy. Subduction‐induced entrained and toroidal flows under the Cascadia margin are discriminated well by the spatial relationship between tilting‐axis anisotropy and slab geometry. The obliquely entrained flow is trapped in a narrow zone (<100 km wide) above and below the subducting slab and reaches ∼200 km depth, which is surrounded by large‐scale sub‐horizontal toroidal flow. The intraslab anisotropy is trench‐normal above 80 km depth but changes to trench‐parallel at 100–400 km depths, which may reflect fossil anisotropy overprinted by deep deformation beneath the arc, or joint effect of serpentinization and hydrous faulting.

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