ヒマラヤ山脈とチベットの下の地震:強力な石層マントルの証拠
1Department of Geology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
まとめ
ヒマラヤとチベットの深い地震は,マントルの石層が強いことを示しています. この強さは,海洋プレート沈下が終わった後でも,張力エネルギーを貯蔵することを可能にします.
科学分野:
- 固体地球地質物理学 固体地球地質物理学
- 地震学 地震学とは
- テキトニックプレートダイナミクス
背景:
- 大陸内地震は,石層の強さと変形を理解するために研究されています.
- 以前の研究は地殻の地震に焦点を当てており,大陸の衝突地帯の深いマントルの出来事についてはあまり知られていない.
研究 の 目的:
- チベットの高原および周辺地域における深層大陸内地震の発生と特性を調査する.
- これらのマントルの地震の深さと,石層の強度に対する影響を決定する.
主な方法:
- 1963年から1999年までの11回の大陸内地震 (マグニチュード4.9~6) の地震波形分析.
- 精密な焦点深さの決定に用いられる高解像度の地震データで,一部の焦点深さは100kmを超えています.
主要な成果:
- 地震は,西ヒマラヤのシンタキシス,西クンルン山脈,チベット南部の下にあるマントル・リトスフィアで記録された.
- 焦点深さは100km以上に達し,厚くなった地殻にもかかわらずマントルの関与を確認しました.
- これらの現象は,海洋の沈殿が数百万年前に停止した地域で起こった.
結論:
- 石層マントルは,有意な弾性ストレスを蓄積することができる.
- マントルの石層の強さは,大陸の衝突地帯の地震性において決定的な役割を果たします.
- これらの発見は,サブドクション後の環境における石層の行動に関する以前の仮定に異議を唱える.
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