期刊
EARTH AND PLANETARY SCIENCE LETTERS
卷 216, 期 4, 页码 693-702出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0012-821X(03)00532-6
关键词
core-mantle boundary; ultra-low velocity zone; lower mantle; nuclear explosions; reflection seismology; long-range explosion seismology
Recent seismological studies have presented evidence for the existence of a layer with ultra-low seismic velocities at the core-mantle boundary at ca. 2900 km depth. We report high-amplitude, high-frequency, and laterally coherent seismic arrivals from three nuclear explosions in Siberia. With recording station intervals of 15 km, the seismic phases are readily correlated and show the presence of a thin, ultra-low velocity zone in a region where it was not previously reported. The duration and complexity of the arrivals are inconsistent with a simple core-mantle boundary and require a hitherto unidentified, kilometre-scale, fine structure in the ultra-low velocity zone. The observations may be explained by a ca. 7 km thick, two-layer, ultra-low velocity zone with exceptional low velocities, which indicate the presence of high percentages of melt (> 15%), in particular in the lower part of the zone. Waveform variation implies lateral change in the thickness and physical properties of the ultra-low velocity zone with a wavelength of less than 100 km. (C) 2003 Elsevier B.V. All rights reserved.
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