Dual subduction tectonics and plate dynamics of central Japan shown by three-dimensional P-wave anisotropic structure
Dual subduction tectonics and plate dynamics of central Japan shown by three-dimensional P-wave anisotropic structure
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DOI：
10.1016/j.pepi.2015.03.008
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发表时间：
2015-07-01
影响因子：
2.3
通讯作者：
Koketsu, Kazuki
中科院分区：
文献类型：
--
作者：
Ishise, Motoko;Miyake, Hiroe;Koketsu, Kazuki
日本中部俯冲带的特点是复杂的构造环境，受到海洋板块的双重俯冲和岛弧之间的碰撞的影响。为了更好地了解俯冲系统，我们进行了各向异性层析成像分析，利用当地地震的P波到达时间，以确定覆盖板块和太平洋和菲律宾海（PHS）板块的P波方位各向异性的三维结构。俯冲板块和俯冲板块各向异性的主要特征是：（1）在俯冲板块，地壳各向异性快方向的分布模式与地质构造走向一致;（2）在两个大洋板块，P波快传播方向与海底扩张方向近平行。此外，我们的层析图像表明，（1）日本最长的断层带--中央构造线的底部延伸到下地壳，似乎与沿着PHS板块的板间地震的震源区相连，（2）PHS板块的分段--伊豆群岛弧、西七户海脊和四国盆地--由于形成历史，反映在各向异性的区域变化上。层析成像研究进一步表明，东京都市区下方可能存在先前研究所提出的太平洋板块碎片。整体研究结果强烈表明，地震各向异性分析提供了潜在的有用信息，了解俯冲带。(C)2015 Elsevier B. V.版权所有。
The central Japanese subduction zone is characterized by a complex tectonic setting affected by the dual subduction of oceanic plates and collisions between the island arcs. To better understand of the subduction system, we performed an anisotropic tomography analysis using P-wave arrival times from local earthquakes to determine the three-dimensional structure of P-wave azimuthal anisotropy in the overriding plate and the Pacific and Philippine Sea (PHS) slabs. The principal characteristics of anisotropy in the subducted and subducting plates are (1) in the overriding plate, the distribution pattern of fast direction of crustal anisotropy coincides with that of the strike of geological structure, (2) in the two oceanic plates, fast propagation directions of P-wave were sub-parallel to the directions of seafloor spreading. Additionally, our tomographic images demonstrate that (1) the bottom of the Median Tectonic Line, the longest fault zone in Japan, reaches to the lower crust, and seems to link to the source region of an inter-plate earthquake along the PHS slab, (2) the segmentation of the PHS slab the Izu Islands arc, the Nishi-Shichito ridge, and the Shikoku basin - due to the formation history, is reflected in the regional variation of anisotropy. The tomographic study further implies that there might be a fragment of the Pacific slab suggested by a previous study beneath the Tokyo metropolitan area. The overall findings strongly indicate that seismic anisotropy analysis provide potentially useful information to understand a subduction zone. (C) 2015 Elsevier B.V. All rights reserved.