カリブ海の下の下層マントルの横向的な異質性
1Department of Geological Sciences, Southern Methodist University, Dallas, TX 75275-0395, USA.
Science (New York, N.Y.)
|September 11, 1999
まとめ
地震波は,地球の中心や最も下位のマントルに反射する際,異常な遅さを示します. これらの異常は,下層マントルの速度構造の重要な横向的な変動を示唆し,標準地球モデルから逸脱しています.
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
- 地球科学 地球科学 地球科学
背景:
- 地震波の伝播は,地球の深層構造を推測するために使用されます.
- IASPEI91モデルは,地震波の移動時間に関する標準的な基準です.
- 異常な地震波の振る舞いは,予想される地球モデルからの偏差を示し得る.
研究 の 目的:
- 特定の地域から観測された地震波の遅さの異常を調査する.
- IASPEI91 標準地球モデルから観測された偏差の原因を特定する.
主な方法:
- 地球の核からの地震波反射の分析.
- カリブ海,ベネズエラ,ミッド・アトランティック・リッジのイベントから北米の配列で地震データを記録する.
- 最下層のマントルで回転するP波を調べる.
主要な成果:
- 観測された地震波の遅さは,IASPEI91モデルによって予測されたものより64%以上大きかった.
- 異常な遅さは,コア反射と最下層マントルのP波の両方に検出されました.
- これらの遅さの異常は,有意な移動時間残留なしに発生しました.
結論:
- 下層マントルの速度構造の横の不均一性は,観測された地震の遅さの異常の原因である可能性が高い.
- この調査結果は,IASPEI91の標準地球モデルの特定の地域における限界を明らかにしている.
- 下層マントルの速度構造に関するさらなる研究が必要である.
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