The Sunda Plate is a minor tectonic plate bounded by tectonically active convergent boundaries, below which are subducting: the Philippine Sea Plate to the east and the Indo‐Australian Plate to the south and west. It is thus an ideal tectonic setting for investigating the interaction between subduction and asthenospheric flow. To better understand mantle interactions within the two nearly perpendicular subduction zones, we characterize seismic anisotropy by conducting a source‐side sS splitting analysis, which allows us to improve spatial resolution of anisotropic fabrics, in particular underneath the backarc regions, which are poorly constrained by previous studies. In the backarc of the Java‐Banda subduction zone, a gradual fast‐axis rotation from trench normal in the west to trench parallel in the east is clearly observed. We attribute this rotation to the interactions between the 2‐D corner flow in the Java wedge and a squeezed asthenospheric flow by the highly arcuate Banda slab. In the backarc of the Philippine subduction zone, the fast‐axis direction transitions from trench normal in the central south to trench oblique in the north; the trench normal is attributed to the mantle wedge corner flow, whereas the trench oblique is likely deflected by the eastward subduction of the South China Sea Plate. Hence, the mantle flow system beneath the Sunda Plate is composed of various types of flow developed in the mantle wedges. Their interactions play an important role in influencing greatly the regional geodynamics in the upper mantle above the 670‐km discontinuity.

中文翻译：

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爪哇-班达和菲律宾俯冲带的地震各向异性及其对Sun他板块下方地幔流系统的影响

da他板块是一个较小的构造板块，受构造活跃的汇聚边界所限，在其下方俯冲：东部是菲律宾海板块，南部和西部是印澳板块。因此，它是研究俯冲与软流圈之间相互作用的理想构造环境。为了更好地理解这两个几乎垂直俯冲带内地幔的相互作用，我们通过进行源极侧表征地震各向异性SS分裂分析，这使我们能够提高各向异性织物的空间分辨率，尤其是后弧区域下方的各向异性织物，而以前的研究很难对此进行限制。在爪哇-班达俯冲带的后弧中，可以清楚地看到从西侧的法线到东侧的平行线逐渐的快轴旋转。我们将此旋转归因于Java楔形中的二维角流与高度弓形的Banda平板压缩的软流圈流之间的相互作用。在菲律宾俯冲带的后弧，快轴方向从中南部的south沟法线过渡到北部的trench沟斜线。沟渠法线归因于地幔楔角流，而沟渠倾斜可能被南海板块向东俯冲所偏转。因此，Sun他板块下方的地幔流动系统由地幔楔中形成的各种类型的流动组成。它们的相互作用在极大地影响670 km不连续面上方上地幔的区域地球动力学方面起着重要作用。