Complex patterns of mantle flow in eastern SE Asian subduction zones inferred from P‐wave anisotropic tomography
Complex patterns of mantle flow in eastern SE Asian subduction zones inferred from P‐wave anisotropic tomography
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P-波各向异性层析成像推断东南亚东部俯冲带地幔流的复杂模式
DOI：
10.1029/2021jb023366
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Yaolin Shi
中科院分区：
文献类型：
--
作者：
Wei Wei;Dapeng Zhao;Weiqian Yu;Yaolin Shi
我们通过从ISC-EHB数据库中选择的大量P波到达时间的反演，确定了东南亚东部的三维各向同性和各向异性P波速度模型。我们的结果揭示了俯冲的南中国海、尼格罗斯、摩鹿加海、菲律宾海和班达板块、先前俯冲的原南海板块和其他古板块的详细结构，显示了这些洋板块在东南亚东部的长期俯冲。沿马尼拉海沟，南海板块俯冲角在18°N处有明显变化。我们认为，南海板块在18°N以南相对较低的倾角是由已灭绝的大洋中脊俯冲造成的，在18°N可能形成了板块撕裂，这一特征得到了地幔楔形P波方位各向异性的分辨快速方向的支持，这表明南海板块南侧可能发育了三维环状地幔流动。三河俯冲带深部地幔楔体中发现了海沟正常的FVD，这与摩鹿加海板块的深俯冲和停滞有关。在摩鹿加海板块下方观察到近海沟平行的FVD，这可能是由于后退的板块或与双面俯冲相关的反射亚板块地幔流动导致的海沟平行伸展所致。俯冲半达板块呈弧形特征，对地幔楔内的流动形态有很大影响。
We determine 3‐D isotropic and anisotropic P‐wave velocity models beneath eastern SE Asia by inverting a large number of P‐wave arrival times selected from the ISC‐EHB database. Our results reveal detailed structures of the subducting South China Sea (SCS), Negros, Molucca Sea, Philippine Sea, and Banda slabs, the previously subducted Proto‐SCS slab and remnants of other paleo slabs, showing long‐lived subductions of these oceanic slabs in eastern SE Asia. There is an obvious change in the subduction angle of the SCS slab at 18°N along the Manila trench. We suggest that the relatively low dip angle of the SCS slab to the south of 18°N was caused by subduction of an extinct mid‐ocean ridge, and a slab tear is possibly formed at 18°N. This feature is supported by the resolved fast velocity directions (FVDs) of P‐wave azimuthal anisotropy in the mantle wedge, which show that 3‐D toroidal mantle flow may develop around the southern part of the SCS slab. Trench‐normal FVDs are revealed in the deeper mantle wedge of the Sangihe subduction zone, which are associated with the deep subduction and stagnancy of the Molucca Sea slab. A nearly trench‐parallel FVD is observed beneath the Molucca Sea slab, which may be caused by trench‐parallel extension due to the retreating slab or reflect subslab mantle flow associated with the double‐sided subduction. The subducting Banda slab exhibits a curved feature, which greatly affects the flow pattern in the mantle wedge.