中国科学院精密测量科学与技术创新研究院倪四道团队，在探测与俯冲板块相关的高速地幔底部的中超低速带中取得新进展。相关论文于2024年3月4日发表于国际顶尖学术期刊《自然—地球科学》杂志上。
研究人员使用在北美、欧洲和中国记录的60个大震源深震事件的地震相SKKKP，及其B-焦散衍射(B-焦散距离以外的SKKKP波)的地球物理观测，以探测核幔边界的超低速带。研究人员分析和模拟了地幔和外核中不同速度异常的扩展SKKKP B-焦散衍射。
除了太平洋中部和非洲下方两个大型低速区周围的超低速带外，研究结果还支持了以前未被勘探的高速地幔底部区域的超低速带，包括中美洲、阿拉斯加、格陵兰岛、西亚和中亚。研究人员认为，在高速地幔底部中存在超低速带的证据，与下地幔深处存在部分熔融的俯冲洋壳是一致的。
据悉，地核—地幔边界地震学观测揭示的超低速带，为揭示地球深部的物理化学特征和动力演化提供了线索。超低速带主要在大型低速区的内部和边缘被探测到。高速地幔底部中的超低速带也有报道，但其全球评估受到数据覆盖的限制。
附：原文原文
Title: Detections of ultralow velocity zones in high-velocity lowermost mantle linked to subducted slabs
Author: Su, Yulong, Ni, Sidao, Zhang, Baolong, Chen, Yulin, Wu, Wenbo, Li, Mingming, Sun, Heping, Hou, Mingqiang, Cui, Xiaoming, Sun, Daoyuan
Issue&Volume: 2024-03-04
Abstract: Ultralow velocity zones revealed by seismological observations at the core–mantle boundary lend clues to the physico-chemical characteristics and dynamic evolution of the Earth’s deep interior. Ultralow velocity zones have been primarily detected within and at the edges of the large low-velocity provinces. Ultralow velocity zones in high-velocity lowermost mantle have also been reported, but global assessment has been limited by data coverage. Here we use geophysical observations of the seismic phase SKKKP and its B-caustic diffractions (SKKKP waves beyond the B-caustic distance) for 60 large and deep-focus events recorded in North America, Europe and China to detect ultralow velocity zones at the core–mantle boundary. We analyse and simulate the extended SKKKP B-caustic diffractions with different velocity anomalies in the mantle and outer core. In addition to ultralow velocity zones around the two large low-velocity provinces beneath the mid-Pacific and Africa, our results support ultralow velocity zones in previously under-explored high-velocity lowermost mantle regions, including Central America, Alaska, Greenland and West and Central Asia. We suggest our evidence for ultralow velocity zones in high-velocity lowermost mantle is consistent with the presence of partially molten subducted oceanic crust at the deep lower mantle.
DOI: 10.1038/s41561-024-01394-5
Source: https://www.nature.com/articles/s41561-024-01394-5