Wang Zewei, Zhao Dapeng
Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Japan.
Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, China.
Sci Adv. 2021 Jan 20;7(4). doi: 10.1126/sciadv.abc9620. Print 2021 Jan.
How mantle materials flow and how intraslab fabrics align in subduction zones are two essential issues for clarifying material recycling between Earth's interior and surface. Investigating seismic anisotropy is one of a few viable technologies that can directly answer these questions. However, the detailed anisotropic structure of subduction zones is still unclear. Under a general hexagonal symmetry anisotropy assumption, we develop a tomographic method to determine a high-resolution three-dimensional (3D) wave anisotropic model of the Japan subduction zone by inverting 1,184,018 travel time data of local and teleseismic events. As a result, the 3D anisotropic structure in and around the dipping Pacific slab is firstly revealed. Our results show that slab deformation plays an important role in both mantle flow and intraslab fabric, and the widely observed trench-parallel anisotropy in the forearc is related to the intraslab deformation during the outer-rise yielding of the subducting plate.
地幔物质如何流动以及俯冲带内板内组构如何排列，是阐明地球内部与地表之间物质循环的两个关键问题。研究地震各向异性是能够直接回答这些问题的少数可行技术之一。然而，俯冲带详细的各向异性结构仍不清楚。在一般六方对称各向异性假设下，我们开发了一种层析成像方法，通过对1184018个地方和远震事件的走时数据进行反演，来确定日本俯冲带的高分辨率三维（3D）波各向异性模型。结果，首次揭示了俯冲太平洋板块及其周围的三维各向异性结构。我们的结果表明，板块变形在地幔流动和板内组构中都起着重要作用，而在弧前广泛观测到的与海沟平行的各向异性与俯冲板块外隆屈服期间的板内变形有关。
