まとめ
地震波の速度のアニソトロピーは,海洋マントルの変形がプレート運動ではなく,海底の広がりとアステノスフィアの流れによって支配されていることを示しています. これは海底の下にある 地球の内部を形作る過程を 明らかにしています
科学分野:
- 地理学
- 地震学
- 構造学
背景:
- プレート運動とマントルのコンベクションは地球の内部を変形させ,地震波の速度アニソトロピーで検出可能な岩層を形成します.
- 海洋上のマントルの変形は,通常は石層の境界近く,特に海底の広がる中心部とアステノスフィアの内部で推論される.
- 地震モデルでは,海底の広がりとアステノスフィアの流れが海洋の石層を変形させるという相対的な重要性について異なる見解を示している.
研究 の 目的:
- 太平洋中部における海洋性石層-アステノスフィアのシステム内の地震性アニソトロピーを,海底地震計データを用いて調査する.
- 海洋プレートの真ん中の変形プロセスに局所的な制約を与える.
- マントルの変形の原動力として海底の広がり,アステノスフィアの流れ,プレートの動きを区別する.
主な方法:
- ノーメルト実験の海底地震計で記録されたレイリー波の分析
- 地震アニソトロピー,特にアジムタルアニソトロピーを海洋の石層とアステノスフィアにマッピングする.
- 海底の広がり方とプレート移動を比較する.
主要な成果:
- アジムタルアニソトロピーは,海底の広がる方向に整合して,高地震速度の蓋で最も強くなります.
- アニゾトロピーの大きさは,地震の真ん中の低速帯で最小値を示し,アステノスフィアの下の深さで増加します.
- 急速な地震の方向は,どんな深さでもプレート運動と相関しない.
結論:
- 浅い海洋マントルの支配的な変形は,リッジ軸のコーナーフローと圧力 / 浮力によるアステノスフィアの流れで起こります.
- アステノスフィアの上のプレート運動による切断変形は,他の変形メカニズムと比較して軽微なプロセスであるように見える.
- 地震アニソトロピーは,海洋的石層-アステノスフィアシステム内の複雑な変形プロセスに関する重要な洞察を提供します.
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