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ノーマルモードとフリーモードの空気は,地球のマントルの速度と密度の横向的な変動に対する重力制約である
1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Science (New York, N.Y.)
|August 24, 1999
まとめ
研究者は地震データと重力異常を用いてマントルの変動をマッピングした. 密度が高い物質は,太平洋とアフリカの下にあるコア・マントルの境界付近に存在し,構成の異質性を示唆しています.
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:
- マントルのダイナミクスを理解することは,プレート構造と地球の熱的進化にとって極めて重要です.
- 以前のモデルは,移動時間と波形の逆転に依存し,深層マントルの構造の解像度が限られていた.
研究 の 目的:
- 地球のマントル内の地震速度と密度の横向的な変動を決定する.
- ダイナミックな地形と660kmとコア-マントルの境界の不連続性をマップする.
主な方法:
- 自由振動の地震データの大規模なデータセットを利用した.
- フリーエア重力異常データからの組み込み制約.
- 地震と重力のデータを組み合わせて,マントルの性質を逆転させる.
主要な成果:
- 切断速度,圧縮速度,密度変化の詳細なモデルを開発しました.
- 太平洋とアフリカの最下層マントルの平均より密度の高い物質の特定された地域.
- 観測された緩やかな切断速度は,これらの密集した領域と相関しており,上流の兆候です.
結論:
- この発見は,コア-マントルの境界付近の組成の異質性の存在を裏付けている.
- これらの異質性は,深層マントルの上流システムと関連しています.
- この研究は,地球の深層構造とダイナミクスの理解を洗練します.
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