大陸上の上層マントルのアジムタルアニソトロピーの深さ分布
Federica Marone1, Barbara Romanowicz
1Berkeley Seismological Laboratory, 209 McCone Hall, Berkeley, California 94720, USA.
Nature
|May 15, 2007
まとめ
上層マントルの地震性アニソトロピーは,2つの異なる層を明らかにします. アステノスフィアのアニソトロピーはプレート運動と一致し,石層のアニソトロピーは北向きの傾向を示し,異なる構造的プロセスを示しています.
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
- 固体地球科学 固体地球科学
背景:
- 地上マントルの地震性アニソトロピーは,おそらく鉱物の方向性によって引き起こされ,石層の形成とテクトニックの活動を反映しています.
- シーア波分裂測定は上層マントルのアニソトロピーを研究するための鍵ですが,低い垂直解像度は,その起源 (石層対アステノ圏) について議論を引き起こします.
- 表面波モデルとシーア波分裂観測の間に不一致がある.
研究 の 目的:
- 地震アニソトロピーの起源に関する議論を,表面波形とシーア波分裂データを統合することによって解決する.
- 北米上層マントルのアニソトロピーの層構造を調査するために.
- アニソトロピー,プレート運動,そして石層厚さの関係を理解するために.
主な方法:
- 表面波形の同時逆転とシーア波分裂データ.
- クラトニックと北米西部の上層マントルの地震性アニソトロピーの分析.
- 異なる深さ (石層とアステノスフィア) での高速軸の指向の特徴化.
主要な成果:
- 北米上層マントルの2つの異なったアニソトロピー層の証拠.
- アステノスフィアの深さ (200〜400 km) で,高速軸はプレート運動の絶対値に準平行しており,現在の地質学プロセスによる切断を示しています.
- リトスフィア (80-200 km) では,高速軸の方向性は,より北向きである.
結論:
- この研究は,二層のアニソトロピック構造を明らかにすることによって,表面波とシーア波の分割データ間の衝突を解決します.
- リソスフィアのアニソトロピーは大きく"凍結"され,明確な方向性を持ち,アステノスフィアのアニソトロピーはプレート運動によって積極的に影響を受けます.
- 構造的に活発な北米西部では,アニソトロピーは,より薄い石層を横断するプレート運動と一致する.
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