Multi-scale anisotropy in NE China: Evidence for localized mantle upwelling
Multi-scale anisotropy in NE China: Evidence for localized mantle upwelling
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DOI：
10.1016/j.epsl.2023.118495
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发表时间：
2024-01
影响因子：
5.3
通讯作者：
Cunrui Han;James O.S. Hammond;M. Ballmer;Wei Wei-Wei;Mijian Xu;Zhouchuan Huang;Liangshu Wang
中科院分区：
文献类型：
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作者：
Cunrui Han;James O.S. Hammond;M. Ballmer;Wei Wei-Wei;Mijian Xu;Zhouchuan Huang;Liangshu Wang
一般认为，太平洋板块的俯冲是中国东北和朝鲜半岛全新世广泛板内火山活动的原因。然而，这一过程如何驱动火山活动，即使它发挥了关键作用，仍然是一个激烈辩论的话题。在这项研究中，使用的地震资料，从中国东北部和朝鲜民主主义人民共和国（朝鲜）北方，我们分析了剪切波分裂转换P到S波在莫霍面（Pms），S波从俯冲板界面（当地S），SKS相位。Pms相位显示出相对较弱的地壳各向异性（<0.25 s），快速极化方向与主要构造特征平行。对于局部S和SKS相位，快极化方向显示出显著的横向变化。我们进一步进行了定量反演，以表明各向异性的深度为150公里，因此，与太平洋俯冲有关的软流圈内的流动驱动。然而，许多空SKS分裂相的存在，以及分散的局部S各向异性在很大范围的入射角表明，垂直流直接在长白山火山下面的本地化区域。这种模式与区域上地幔地震速度结构相对应，表明长白山地区火山活动是由起源较深的局部上升流驱动的。此外，我们推断，这地幔上涌偏转到西南下方长白山和不对称的扩展在岩石圈的底部，可能是因为在该地区的火山活动的历史悠久。
It is commonly proposed that the subduction of the Pacific plate has been responsible for widespread Holocene intraplate volcanism across NE China and the Korean Peninsula. Yet, how this process drives volcanism and even if it plays a critical role remains a topic of vigorous debate. In this study, using seismic data from four networks across NE China and northern Democratic People's Republic of Korea (DPRK), we analyze shear wave splitting in converted P to S-waves at the Moho (Pms), S-waves from the subducted slab interface (local S), and SKS phases. The Pms phases show a relatively weak crustal anisotropy (<0.25 s), with fast polarization directions aligned sub-parallel to major tectonic features. For the local S and SKS phases, fast polarization directions show significant lateral variations. We further perform a quantitative inversion to show that the depth of the anisotropy is ∼150 km, thus driven by flow within the asthenosphere associated with Pacific subduction. However, the presence of many null SKS splitting phases, together with scattered local S anisotropy across a wide range of incidence angles suggests a localized region of vertical flow directly beneath Changbaishan volcano. Such patterns correspond well to regional upper-mantle seismic velocity structure, and suggest that a localized upwelling with a relatively deep origin drives volcanism in the Changbaishan region. Furthermore, we infer that this mantle upwelling is deflected to the SW beneath Changbaishan and spreads asymmetrically at the base of the lithosphere, possibly because of the long history of volcanism in the region.