地球最下層マントルの変数アジムタルアニソトロピー
Edward J Garnero1, Valérie Maupin, Thorne Lay
1Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-1404, USA. garnero@asu.edu
Science (New York, N.Y.)
|October 9, 2004
まとめ
地震波の極性逆転は,地球のコア-マントルの境界で,深層マントルのアニソトロピーを示唆しています. これらの発見は,マントルのコンベクションによって引き起こされる可能性のあるD'層の鉱物並びを示しています.
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
- ミネラル物理学 ミネラル物理学
背景:
- 地球の最も下位のマントルであるD'層は,複雑な地震特性を示しています.
- シェア波分裂と極性逆転は,地震性アニソトロピーの重要な指標である.
研究 の 目的:
- D'層で観察された絶え間ないシェア波の極性逆転の原因を調査する.
- マントルの底辺におけるアジムタルアニソトロピーの度数とパターンを決定する.
主な方法:
- カリブ海の下の地震経路のための分割切断波の完全な波形モデリング.
- 地震波の振る舞いの分析,特に垂直と水平に偏振されたシーザー波.
主要な成果:
- 観測されたシェア波の極性逆転は,水平に偏ったシェア波の到来と相関する.
- マントルの底部におけるアジムタルアニソトロピーは,分割された切断波を説明するために必要である.
- データと一致するモデルは,傾斜した六角対称性軸 (最大20度) の横断イソトロピーを示しています.
結論:
- 観測された地震現象は,D'層内の横向きに変動する鉱物配列 (結晶学または形状の好みの方向) を示している.
- D'層の上の小規模なマントルのコンベクション細胞は,おそらくこれらの変化を誘導し,鉱物の方向性に影響を与える.
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