Ishii Miaki, Dziewoński Adam M
Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA.
Proc Natl Acad Sci U S A. 2002 Oct 29;99(22):14026-30. doi: 10.1073/pnas.172508499. Epub 2002 Oct 8.
Since the discovery of the inner core in 1936, no additional spherical subshell of the Earth has been observed. Based on an extensive seismic data set, we propose the existence of an innermost inner core, with a radius of approximately 300 km, that exhibits a distinct transverse isotropy relative to the bulk inner core. Specifically, within the innermost inner core, the slowest direction of wave propagation is approximately 45 degrees from the east-west direction. In contrast, the direction of the slowest wave propagation in the overlying inner core is east-west. The distinct anisotropy at the center of the Earth may represent fossil evidence of a unique early history of inner-core evolution.
自1936年发现内核以来，尚未观测到地球的其他球形子壳层。基于大量地震数据集，我们提出存在一个最内层内核，其半径约为300公里，相对于整体内核表现出明显的横向各向异性。具体而言，在最内层内核中，波传播最慢的方向与东西方向大约成45度角。相比之下，上覆内核中波传播最慢的方向是东西方向。地球中心明显的各向异性可能代表了内核演化独特早期历史的化石证据。
