近日，美国南加州大学Vidale John E.团队在研究地震波形变化反转的内核回溯中取得新进展。相关论文于2024年6月12日发表于国际顶尖学术期刊《自然》杂志上。

据悉，固体的内核悬浮在液体的外核中，并通过重力固定，根据重复地震和爆炸产生的地震记录的变化，可以推断出固体内核相对于地球表面旋转或在几年到几十年内发生变化。它具有丰富的内部结构，并影响外核对流的模式，从而影响地球磁场。

研究团队汇编了143对不同的重复地震数据，其中许多发生在16次多重地震中，这些地震由1991年至2023年南桑威奇群岛的121次地震组成。研究分析了北美北部中等缝隙阵列记录的穿透内核的PKIKP波。研究人员还记录了许多多重谱线表现出变化的波形，然后在稍后的时间恢复以匹配早期事件。匹配的波形揭示了内核相对于地幔重新占据相同位置的时间（就像过去的某个时间一样）。

匹配模式以及之前的研究表明，从2003年到2008年，内核逐渐超旋转，然后从2008年到2023年以更缓慢的速度次旋转2到3次回到同样的路径。这些匹配能够精确和明确地跟踪内核的进展和回归。对不同的前后运动速率的解析表明，需要建立新的模型来研究地核、外核和地幔之间的动力学过程。

附：英文原文

Title: Inner core backtracking by seismic waveform change reversals

Author: Wang, Wei, Vidale, John E., Pang, Guanning, Koper, Keith D., Wang, Ruoyan

Issue&Volume: 2024-06-12

Abstract: The solid inner core, suspended within the liquid outer core and anchored by gravity, has been inferred to rotate relative to the surface of Earth or change over years to decades based on changes in seismograms from repeating earthquakes and explosions. It has a rich inner structure and influences the pattern of outer core convection and therefore Earth’s magnetic field. Here we compile 143 distinct pairs of repeating earthquakes, many within 16 multiplets, built from 121 earthquakes between 1991 and 2023 in the South Sandwich Islands. We analyse their inner-core-penetrating PKIKP waves recorded on the medium-aperture arrays in northern North America. We document that many multiplets exhibit waveforms that change and then revert at later times to match earlier events. The matching waveforms reveal times at which the inner core re-occupies the same position, relative to the mantle, as it did at some time in the past. The pattern of matches, together with previous studies, demonstrates that the inner core gradually super-rotated from 2003 to 2008, and then from 2008 to 2023 sub-rotated two to three times more slowly back through the same path. These matches enable precise and unambiguous tracking of inner core progression and regression. The resolved different rates of forward and backward motion suggest that new models will be necessary for the dynamics between the inner core, outer core and mantle.

DOI: 10.1038/s41586-024-07536-4

Source: https://www.nature.com/articles/s41586-024-07536-4