Kaviani Ayoub, Mahmoodabadi Meysam, Rümpker Georg, Pilia Simone, Tatar Mohammad, Nilfouroushan Faramarz, Yamini-Fard Farzam, Moradi Ali, Ali Mohammed Y
Institute of Geosciences, Goethe University, Frankfurt, Germany.
International Institute of Earthquake Engineering and Seismology, Tehran, Iran.
Sci Rep. 2021 Feb 2;11(1):2848. doi: 10.1038/s41598-021-81541-9.
Previous investigation of seismic anisotropy indicates the presence of a simple mantle flow regime beneath the Turkish-Anatolian Plateau and Arabian Plate. Numerical modeling suggests that this simple flow is a component of a large-scale global mantle flow associated with the African superplume, which plays a key role in the geodynamic framework of the Arabia-Eurasia continental collision zone. However, the extent and impact of the flow pattern farther east beneath the Iranian Plateau and Zagros remains unclear. While the relatively smoothly varying lithospheric thickness beneath the Anatolian Plateau and Arabian Plate allows progress of the simple mantle flow, the variable lithospheric thickness across the Iranian Plateau is expected to impose additional boundary conditions on the mantle flow field. In this study, for the first time, we use an unprecedented data set of seismic waveforms from a network of 245 seismic stations to examine the mantle flow pattern and lithospheric deformation over the entire region of the Iranian Plateau and Zagros by investigation of seismic anisotropy. We also examine the correlation between the pattern of seismic anisotropy, plate motion using GPS velocities and surface strain fields. Our study reveals a complex pattern of seismic anisotropy that implies a similarly complex mantle flow field. The pattern of seismic anisotropy suggests that the regional simple mantle flow beneath the Arabian Platform and eastern Turkey deflects as a circular flow around the thick Zagros lithosphere. This circular flow merges into a toroidal component beneath the NW Zagros that is likely an indicator of a lateral discontinuity in the lithosphere. Our examination also suggests that the main lithospheric deformation in the Zagros occurs as an axial shortening across the belt, whereas in the eastern Alborz and Kopeh-Dagh a belt-parallel horizontal lithospheric deformation plays a major role.
先前对地震各向异性的研究表明，在土耳其-安纳托利亚高原和阿拉伯板块之下存在一种简单的地幔流模式。数值模拟表明，这种简单的地幔流是与非洲超级地幔柱相关的大规模全球地幔流的一个组成部分，它在阿拉伯-欧亚大陆碰撞带的地球动力学框架中起着关键作用。然而，在伊朗高原和扎格罗斯山脉之下更东部的地幔流模式的范围和影响仍不清楚。虽然安纳托利亚高原和阿拉伯板块之下相对平滑变化的岩石圈厚度有利于简单地幔流的发展，但预计伊朗高原上变化的岩石圈厚度会给地幔流场施加额外的边界条件。在本研究中，我们首次使用了由245个地震台站组成的网络所记录的前所未有的地震波形数据集，通过研究地震各向异性来考察伊朗高原和扎格罗斯山脉整个区域的地幔流模式和岩石圈变形。我们还研究了地震各向异性模式、利用GPS速度得到的板块运动以及地表应变场之间的相关性。我们的研究揭示了一个复杂的地震各向异性模式，这意味着存在一个同样复杂的地幔流场。地震各向异性模式表明，阿拉伯台地和土耳其东部之下的区域简单地幔流围绕扎格罗斯厚岩石圈呈环形流动。这种环形流在扎格罗斯山脉西北部之下合并为一个环形分量，这可能是岩石圈横向不连续的一个指标。我们的研究还表明，扎格罗斯山脉主要的岩石圈变形表现为沿山脉轴向的缩短，而在东阿尔伯兹山脉和科佩特山脉，与山脉平行的水平岩石圈变形起主要作用。
