在大陆上层地幔中,亚齐木特异性深度分布
Federica Marone1, Barbara Romanowicz
1Berkeley Seismological Laboratory, 209 McCone Hall, Berkeley, California 94720, USA.
Nature
|May 15, 2007
概括
上层地幔的地震异构性揭示了两个不同的层. 星球异构与板块运动保持一致,而岩层异构则显示出朝北的趋势,表明不同的构造过程.
科学领域:
- 地质物理学 地质物理学
- 地震学 地震学
- 固体地球科学 固体地球科学
背景情况:
- 地球上层地幔的地震异构,可能是由于矿物质的方向造成的,反映了石层的形成和构造活动.
- 剪波分裂测量是研究上层地幔异性质的关键,但垂直分辨率差导致了关于其起源 (石化层与化层) 的争论.
- 表面波模型和剪切波分裂观测之间存在差异.
研究的目的:
- 通过整合表面波形和剪切波分裂数据来解决关于地震异构性起源的辩论.
- 为了研究北美上层地幔中异构的分层结构.
- 为了理解异构性,板块运动和石质层厚度之间的关系.
主要方法:
- 表面波形和剪切波分裂数据的同时反转.
- 在克拉顿和北美西部上层地幔中对地震异构的分析.
- 在不同深度 (石化层和石化层) 的快速轴方向的表征.
主要成果:
- 证据表明北美上层地幔有两个不同的异构层,不同的快速轴方向.
- 在星球深度 (200-400公里) 中,快速轴与绝对板块运动相平行,表明来自当前构造过程的剪切.
- 在石灰岩层 (80-200公里),快速轴的方向显著更朝北.
结论:
- 这项研究通过揭示两层异构结构来解决表面波和剪波分裂数据之间的冲突.
- 石层的异构性在很大程度上是"结"的,具有明显的方向,而天层的异构性则受到板块运动的积极影响.
- 在构造学上活跃的北美西部,异构性与板块运动在较薄的石化层上保持一致.
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