核の頂部にある硬いゾーンの地震検出
1Department of Earth Sciences, University of California, Santa Cruz, CA 95064, USA. srost@es.ucsc.edu
まとめ
地震データは,地球の外核の上部にある硬いゾーンを明らかにしています. これらの薄い,固体鉄に富んだ層は,地球のニュテーションと外部のコアのコンベクションに影響を与える可能性があります.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- 地震学 地震学とは
- 地球科学 地球科学 地球科学
背景:
- 地球の外核は主に液体鉄とニッケルで構成されています.
- 核-マントルの境界を理解することは,地震波の伝播を解釈する上で極めて重要です.
- 以前の研究では,コア-マントルの境界で異質性が示唆されていた.
研究 の 目的:
- 最上端の外核の物理的性質を調査する.
- コア-マントルの境界で潜在的な硬い構造を特定する.
- これらの構造が地球の動力学に及ぼす影響を調査する.
主な方法:
- オーストラリア北部で記録されたトンガ・フィジーの地震による地震波の分析.
- 外核の性質を推論するために,ScP波形のモデリング.
- 地震配列データを活用して,最も外側のコアにおけるS波の拡散を検出する.
主要な成果:
- 外核の頂上にある薄い (0.12-0.18 km) 硬いゾーンの証拠.
- これらのゾーンは,S波の伝播を可能にする小さな,正のS波速度 (0.6-0.8 km/s) を表しています.
- ゾーンは,固体材料と混合された溶鉄としてモデル化されています.
結論:
- 特定された硬いゾーンは,コア-マントルの境界の地形上の高さを表す可能性があります.
- これらの特徴は,軽い核の堆積物で満たされる可能性があります.
- ゾーンは,地球の核の変動や外核のコンベクションに重要な役割を果たす可能性があります.
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