カリフォルニア湾の下のマントルのコンベクティブ上流は,カリフォルニア湾の下にある
Yun Wang1, Donald W Forsyth, Brian Savage
1Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA. yun_wang@brown.edu
Nature
|November 27, 2009
まとめ
地震画像は,カリフォルニア湾の部分的な融解を明らかにしています.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- テクトニクス (地質学) とは
- マントラダイナミクス マントラダイナミクス
背景:
- バヤ・カリフォルニア州は,過去600万年にわたって北アメリカから分離し,カリフォルニア湾を形成した.
- カリフォルニア湾は海底が広がるユニークなシステムで,密度の高い地震覆面があり,上層マントルの詳細な研究を可能にします.
研究 の 目的:
- 拡散センターの下の浅いマントルの動的および被動的な上流の相対的な役割を調査する.
- カリフォルニア湾の上層マントルの構造を地震トモグラフィを用いてイメージする.
主な方法:
- レイリー波トモグラフィーは,上層マントルのシーア波速度をマッピングするために使用されました (約. 200kmの深さ).
- 解析は,カリフォルニア湾の密集した地震計ネットワークからの地震データに焦点を当てた.
主要な成果:
- 海洋の拡散センターの特徴である低シア速度が湾岸全体で観測されました.
- 異常に低い切断速度の3つの異なるゾーンが特定され,約250kmの距離が隔てられていた.
- 40〜90kmの深さにあるこれらの異常は,マントルの被動的な上流が融解を開始すると予想される深さと相関しています.
結論:
- 部分的な融解は,カリフォルニア湾の下の浅いマントルの動的上流を誘発しているようです.
- このダイナミックな上流は,溶融浮力や,マントルの枯渇した物質の密度の低下によって引き起こされる可能性が高い.
- この発見は,ホットスポットが支配するシステムとは異なる,拡散センターにおけるマントルのプロセスを理解するのに寄与する.
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