美国加州大学洛杉矶分校John E. Vidale团队研究了地球内核自转速度和近地表的年尺度变化。相关论文于2025年2月10日发表在《自然—地球科学》杂志上。
自发现穿越内核的重复地震引起的地震波的时间变化以来，人们一直推断内核会在几年到几十年内改变其旋转速度或形状。最近的研究证实，在过去的几十年里，内核的旋转速度比地球其他部分快，然后变慢；这项工作分析了1991年至2023年间南桑威奇群岛发生的121对重复地震事件的穿越内核（PKIKP）地震波，通过北美北部的艾尔森（ILAR）和黄刀（YKA）阵列记录。
研究组扩展了这组重复的地震，并比较了内核重新占据相同位置时的地震对，揭示了2004年至2008年间YKA而非ILAR的非旋转变化。研究组认为这些变化起源于浅层内核，因此对内核掠YKA射线路径的影响大于对ILAR的深层底层射线路径的影响。因此，研究组解决了长期以来关于PKIKP波的时间变化是由旋转还是内核边界附近的更多局部作用引起的争论：暂定两者兼而有之。内核边界附近的变化很可能由边界地形与地幔密度异常耦合驱动的粘质变形或外核对流对内核的牵引引起。
附：英文原文
Title: Annual-scale variability in both the rotation rate and near surface of Earth’s inner core
Author: Vidale, John E., Wang, Wei, Wang, Ruoyan, Pang, Guanning, Koper, Keith
Issue&Volume: 2025-02-10
Abstract: The inner core has been inferred to change its rotation rate or shape over years to decades since the discovery of temporal variability in seismic waves from repeating earthquakes that travelled through the inner core. Recent work confirmed that the inner core rotated faster and then slower than the rest of Earth in the last few decades; this work analysed inner-core-traversing (PKIKP) seismic waves recorded by the Eielson (ILAR) and Yellowknife (YKA) arrays in northern North America from 121 repeating earthquake pairs between 1991 and 2023 in the South Sandwich Islands. Here we extend this set of repeating earthquakes and compare pairs at times when the inner core re-occupied the same position, revealing non-rotational changes at YKA but not ILAR between 2004 and 2008. We propose that these changes originate in the shallow inner core, and so affect the inner-core-grazing YKA ray paths more than the deeper-bottoming ray paths to ILAR. We thus resolve the long-standing debate on whether temporal variability in PKIKP waves results from rotation or more local action near the inner-core boundary: it is tentatively both. The changes near the inner-core boundary most likely result from viscous deformation driven by coupling between boundary topography and mantle density anomalies or traction on the inner core from outer-core convection.
DOI: 10.1038/s41561-025-01642-2
Source: https://www.nature.com/articles/s41561-025-01642-2