地震アニソトロピーによる最下層マントルの変形
Andy Nowacki1, James Wookey, J-Michael Kendall
1Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK. andy.nowacki@bristol.ac.uk
Nature
|October 29, 2010
まとめ
地球のD′′層における地震性アニソトロピーは,MgSiO(3) のペロブスキート後の変形を示唆している. 新しい測定は,地震波の分裂を説明するために複雑なメカニズムが必要であることを明らかにし, (001) のシアをおそらくの原因として指摘しています.
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:
- 地球の最も下層のマントル (D′′) は,重要な地震性アニソトロピーを示しています.
- このアニソトロピーは,支配的な鉱物相であるMgSiO ((3) - ポストペロブスキート (ppv) の配列によって引き起こされる可能性があります.
- 以前のアニソトロピーの測定は範囲が限られており,PPV変形機構の理解を妨げていた.
研究 の 目的:
- 北米と中米の下のD′′層における地震性アニソトロピーを調査する.
- MgSiO (((3) -ppv.における滑り込みの候補メカニズムを区別する.
- コア・マントル境界における変形過程の理解を向上させる.
主な方法:
- 浅と深い地震の両方を用いて,D′′層におけるシェア波分裂の測定.
- アジムタル範囲を拡大した3つの地域における700以上の測定値の取得.
- 観測された地震データに対して様々なMgSiO(3) -ppv変形メカニズムをテストする.
主要な成果:
- D"の垂直横断イソトロピーモデルが以前から想定されていたのは,データによって支持されていません.
- 観測された地震性アニソトロピーを説明するために,より複雑な変形メカニズムが必要である.
- MgSiO(3) -ppvの (001) 平面でのシーアは,観測されたアニソトロピーの最も一貫した説明である.
結論:
- この発見は,D′′層における地震性アニソトロピーのより単純なモデルに異議を唱えている.
- (001) のシーアが,MgSiO(3) -ppv.の最も可能性の高い変形メカニズムとして特定されています.
- この研究は,コア-マントルの境界で変形をマップする経路を提供し,D′′プロセスをマントルの動力学とリンクします.
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