在北美东部下方的图像中,一道尖的石化层-石化层边界
Catherine A Rychert1, Karen M Fischer, Stéphane Rondenay
1Department of Geological Sciences, Brown University, Box 1846, Providence, Rhode Island 02912, USA. Catherine_Rychert@Brown.edu
Nature
|July 29, 2005
概括
石化层-石化层边界比预期的要尖,这表明部分融化或挥发性物质,而不仅仅是温度,削弱了石化层. 这种地震成像揭示了对地球地幔动态的关键见解.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 构造学 构造学 构造学 构造学
背景情况:
- 板块构造学依赖于石化层在天气层上的运动.
- 石化层-石化层边界的性质对于理解机械强度差异至关重要.
- 这一边界的地震速度梯度为物理和化学性质提供了洞察力.
研究的目的:
- 使用地震数据调查石化层-石化层边界的度.
- 限制对边界特征负责的物理和化学性质.
- 要区分热和组成/化驱动的减弱机制.
主要方法:
- 在北美东部转换的地震相的分析.
- 在石层底部的地震速度梯度的成像.
- 在特定深度范围内量化剪切波速度下降.
主要成果:
- 在石层-石层边界 (90-110公里深) 观测到一个尖的地震速度梯度.
- 剪切波速度在11公里或更短的时间内下降了3-11%.
- 这种尖的边界与纯粹的热梯度不一致.
结论:
- 天气层可能含有百分之几的部分化物或是富含挥发性物质的.
- 这些因素,而不仅仅是温度,解释了天气层的弱点.
- 这些发现完善了地幔流和板块构造学模型.
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