固体コンベクションによる地球の下層マントルのアニソトロピック構造の発達
Allen K McNamara1, Peter E van Keken, Shun-Ichiro Karato
1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063, USA. mcnamar@umich.edu
Nature
|March 22, 2002
まとめ
コア・マントルの境界線と衝突する沈殿した構造板は,地球の下層マントルの強い地震性アニソトロピーを引き起こします. この変形は鉱物を並べ,特に環太平洋地域では観測可能なアニゾトロピックパッチを生成します.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- ミネラル物理学 ミネラル物理学
- 地震学 地震学とは
背景:
- 地震観測は,地球の下層マントルの底部に高度にアニソトロピックなパッチを示し,大抵の同otropic bulk mantle と対比しています.
- これらのアニソトロピック領域は,過去の潜水やマントルの羽根の上流から発生すると仮定されていますが,アニソトロピーの原因は不明です.
- 提案されたメカニズムには,異質な材料の形状偏好指向 (SPO) または同質な材料の格子偏好指向 (LPO) が含まれており,異なる地動力学的プロセスを意味しています.
研究 の 目的:
- 下層マントルの異なるアニソトロピーメカニズムによる地動力学的影響を調査する.
- 沈殿したスラブの大張力変形が観測された地震性アニソトロピーを説明できるかどうかを判断する.
- ミネラルファブリックの発達と地震性アニソトロピーへの貢献をモデリングする.
主な方法:
- 弾力性の鉱物物理を組み込んだ数値モデリング.
- 固体変形による格子偏好方向 (LPO) の発展をモデリングする.
- 沈下したスラブとコア-マントルの境界との衝突をシミュレートする.
主要な成果:
- この研究は,深い下層マントルのスラブ変形が強い地震性アニソトロピーを生み出せることを示しています.
- 化学的に均質なマントル材料に基づいた開発されたモデルは,高いストレス下での大ストレスの変形から生じるアニソトロピーを示しています.
- このメカニズムは,環太平洋地域の観測されたアニソトロピーを効果的に説明します.
結論:
- 化学的に均質なマントルの材料の固体変形,特にコアマントルの境界と衝突する沈殿板は,下部マントルの地震性アニソトロピーの実行可能な原因です.
- 高張力下での大張力変形による格子偏向 (LPO) は,これらの領域で強いアニソトロピーを生成する支配的なメカニズムである.
- この発見は,地震学的観測と地球マントルの底辺で発生する地動力学的過程を調和させています.
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