An initial map of fine-scale heterogeneity in the Earth’s inner core
An initial map of fine-scale heterogeneity in the Earth’s inner core
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DOI：
10.1038/s41561-022-00903-8
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发表时间：
2022-02
影响因子：
18.3
通讯作者：
Wei Wang;J. Vidale
中科院分区：
文献类型：
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作者：
Wei Wang;J. Vidale
地球内核的地震学特性是了解其组成、动力学和生长历史的关键。在内核内，细尺度的不均匀性先前已被确定从高频压缩波的反向散射。在这里，我们使用历史地震和爆炸数据从大孔径地震阵列，美国，在1969年和1975年之间建立一个三维地图的异质性从内核边界到500公里的深度，并确定的地理分布的散射体在40%的内核是可见的阵列。我们的模型有两个强散射区域，一个在东亚下面，另一个在南美洲下面，这两个区域都位于过去的本地调查已经确定的散射区域。我们认为，这些位点的强大，精细尺度的异质性可能与随机排列的小，内核晶体由于快速冻结。这些地区，已被确定为具有高衰减，并位于较冷的地区的核-幔边界，潜在地提供约束的动态内核和运动的外核，在地幔和外核的下沉可能与强散射和内核的异质性。
The seismological properties of Earth’s inner core are key to understanding its composition, dynamics and growth history. Within the inner core, fine-scale heterogeneity has previously been identified from backscattering of high-frequency compressional waves. Here we use historical earthquake and explosion data from the Large Aperture Seismic Array, USA, between 1969 and 1975 to build a 3D map of heterogeneity from the inner-core boundary to 500 km depth and determine the geographical distribution of the scatterers across the 40% of the inner core that is visible to the array. Our model has two regions of strong scattering, one beneath eastern Asia and the other beneath South America, both located where past local surveys have identified scattering. We suggest that these loci of strong, fine-scale heterogeneities may be related to random alignments of small, inner-core crystals due to fast freezing. These areas, which have been identified as having high attenuation and lie beneath colder areas of the core–mantle boundary, potentially provide constraints on the dynamics of the inner core and the motions in the outer core, with downwelling in the mantle and outer core possibly associated with strong scattering and inner-core heterogeneity.