Widespread seismic anisotropy in Earth’s lowermost mantle beneath the Atlantic and Siberia
Widespread seismic anisotropy in Earth’s lowermost mantle beneath the Atlantic and Siberia
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DOI：
10.1130/g45514.1
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发表时间：
2019-02
期刊：
影响因子：
5.8
通讯作者：
M. Grund;J. Ritter
中科院分区：
文献类型：
--
作者：
M. Grund;J. Ritter
在地球深处，大约2700公里深的核-地幔边界上方，大规模的地幔结构被认为对全球地球动力学过程起着关键作用。虽然异常热区是由上升的地幔热柱和火山热区提供的，但俯冲岩石圈板块的积累与低于平均水平的特征有关。在这两种环境中，地震各向异性的存在可以直接推断出形变和地幔流动等动力驱动过程的出现。然而，这些巨大的异常结构与周围地幔物质的几何形状以及相互作用仍在争论中。基于来自斯堪的纳维亚密集大口径记录网络的新地震资料，我们利用明显不一致的SKS-SKKS剪切波分裂测量结果，描述了地幔下部两个迄今尚未探测的区域的各向异性特征。由此，我们可以证明各向异性位于非洲下方大的低剪切速度省的北缘。此外，我们在西伯利亚地下地震速度较快的区域恢复了各向异性结构，这为深俯冲板块造成的广泛变形提供了额外的证据。
Deep inside the Earth, just above the core-mantle boundary at around 2,700 km depth, large-scale mantle structures are assumed to play a key role for global geodynamic processes. While unusual hot regions are attributed to feed rising mantle plumes and volcanic hotspots, the accumulation of subducted lithospheric plates is associated with colder than average features. In both environments the appearance of dynamic-driven processes such as deformation and mantle flow can directly be inferred by the presence of seismic anisotropy. However, the geometries as well as the interactions of these massive anomalous structures with the surrounding mantle material are still under debate. Based on new seismic data from a dense and large-aperture recording network in Scandinavia we characterize the anisotropic signatures of two so far unexplored regions in the lowermost mantle by using observations of clearly discrepant SKS-SKKS shear wave splitting measurements. Thereby we can demonstrate that anisotropy is located along the northern edges of the Large Low Shear Velocity Province beneath Africa. Furthermore, we recover an anisotropic structure in a region of fast seismic velocity underneath Siberia which provides additional evidence for widespread deformation caused by a deeply subducted slab.