The Transportable Array in south-central Alaska spans several subduction zone features: backarc, forearc and volcanic arc, making it an ideal tool to study subduction zone anisotropy. Shear wave splitting analysis of 157 local earthquakes of m_b ≥ 3.0 that occurred between 2014 and 2019 yields 210 high-quality measurements at 23 stations. Splitting delay times (δt) are generally small (δt ≈ 0.3 s), increasing with distance from the trench. Arc-parallel fast directions, ϕ, are only seen in the forearc, but rotate to arc-perpendicular ϕ in the backarc. Observed ϕ values generally do not parallel teleseismic SKS splitting results, implying that the latter is sensitive primarily to subslab mantle flow, not mantle wedge dynamics. The forearc local-earthquake signal likely originates from anisotropic serpentinite in fractures atop the subducting Pacific Plate, with possible additional signal coming from fractures in the North American crust. Mantle wedge corner flow, potentially with additional arc-perpendicular anisotropy in the subducting slab, explains backarc anisotropy.

中文翻译：

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阿拉斯加中南部地震各向异性的发展：局部地震剪切波分裂的证据

阿拉斯加中南部的可移动阵列跨越了几个俯冲带特征：后弧，前臂和火山弧，使其成为研究俯冲带各向异性的理想工具。的157级本地的地震剪切波分裂分析米_b ≥3.0发生高质量测量2014和产量之间2019 210在23个站。分割延迟时间（δt）通常很小（δt≈0.3 s），随着与沟槽距离的增加而增加。弧平行的快速方向only仅在前臂中可见，但在后弧中旋转为弧垂直ϕ。观测到的generally值通常不与远震SKS分裂结果平行，这意味着后者主要对板下地幔流敏感，而不对地幔楔形动力学敏感。前臂局部地震信号可能源自俯冲太平洋板块顶部裂缝中的各向异性蛇纹岩，可能还有其他信号来自北美地壳裂缝。俯冲板中的地幔楔角流（可能带有附加的垂直弧各向异性）解释了弧后各向异性。