大規模な地震は,孤立したプレート境界断層で定期的に発生します
Kelvin R Berryman1, Ursula A Cochran, Kate J Clark
1GNS Science, Post Office Box 30-368, Lower Hutt 5040, New Zealand. k.berryman@gns.cri.nz
まとめ
長期の地震記録は稀で,再発の行動に関する研究を妨げている. ニュージーランドのアルプス断層に関するこの研究は,8000年以上にわたってほぼ定期的に大規模な地震が再発していることを明らかにし,同様の断層の時間依存の地震リスクモデルを支持しています.
科学分野:
- パレオシズモロジー (Paleoseismology) とは
- 地質物理学 地質物理学とは地質物理学です.
- テクトニクス (地質学) とは
背景:
- 大規模な地震の限られた地質学的記録は,地震の再発パターン (定期的,ランダム,またはクラスター) の理解を複雑にする.
- ニュージーランドにあるアルプス断層は,大きなストライクスライド断層で,滑り率が高く,プレート境界の大きな動きに対応します.
研究 の 目的:
- アルプス断層における大規模な地震の長期記録 (8000年) を再構築する.
- 地震の再発行動に関する仮説を検証する (通常の対ランダム/クラスタ).
- 地震リスクの推定のための時間依存の地震再発モデルの適用性を評価する.
主な方法:
- ホクリ・クリークにおける断層近接堆積物の発掘と分析.
- ストラティグラフィックとジオクロノロジック技術を用いた古地震層の年代測定.
- 地震の再発間隔の統計分析. 地震の再発間隔の統計分析.
主要な成果:
- アルプス断層の24回の表面破裂地震の8000年の記録が確立されました.
- 再発間隔の変数係数は0.33で計算され,ほぼ規則的な行動を示しています.
- 観測された規則性は,断層の単純な幾何学,高滑り率,孤立した振る舞いに起因する.
結論:
- アルプス断層は,ほぼ定期的に大きな地震が再発することを示しています.
- 時間依存の地震再発モデルは,類似の孤立した,高滑り率のストライクスリップ断層の地震リスク評価に適しています.
- この研究は,地震の行動を理解し,地球規模で地震リスクモデルを改善するための貴重な洞察を提供します.
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