推断地球地幔底部的流动,基于地震异构的推理
Mark Panning1, Barbara Romanowicz
1Berkeley Seismological Laboratory, 215 McCone Hall, University of California, Berkeley, CA 94720, USA. mpanning@seismo.berkeley.edu
概括
全球波形断层扫描揭示了整个地幔的辐射异构性. 在核心-地幔边界附近,水平极化S波速度 (VSH) 比垂直极化S波速度 (VSV) 快,表明水平剪切并确认D"区域作为机械边界层.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 地球科学 地球科学 地球科学
背景情况:
- 了解地幔动力学对于理解板块构造学和地球的热演变至关重要.
- 在地震波速的辐射异质性为地幔流和变形提供了洞察力.
- 核心-地幔边界的D"区域是研究地幔-核心相互作用的关键区域.
研究的目的:
- 为了在地球整个地幔中建模辐射异构.
- 为了研究D"区域内的机械特性和流动模式.
- 为了识别与像超级羽毛一样的大规模地幔结构相关的地震特征.
主要方法:
- 全球波形断层扫描的应用.
- 对地震波速度的分析,特别是水平极化S波 (VSH) 和垂直极化S波 (VSV) 速度.
- 在整个地幔中建模辐射异质性.
主要成果:
- 在D"区域检测到横断剪切的大规模占主导地位,VSH速度大约比VSV速度快1%.
- 证实D"区域是地幔对流的机械边界层.
- 在太平洋和非洲超级羽毛下面的无otropic 模式表明垂直流的开始,偏离平均水平剪切签名.
结论:
- D"区域表现出显著的辐射异构,表明水平剪切及其作为机械边界层的作用.
- 地震异质性为下层地幔内不同的流动模式提供了证据,包括与超级羽毛相关的垂直流动.
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