大規模な地震が自己回復するパルスや軽度の亀裂として広がる
Valère Lambert1, Nadia Lapusta2,3, Stephen Perry2
1Seismological Laboratory, California Institute of Technology, Pasadena, CA, USA. vlambert@caltech.edu.
Nature
|March 11, 2021
まとめ
熟成した断層は 低ストレスで大きな地震を招く. 数値モデリングは,持続的に弱い断層は,より高い放射能を生成する自己回復パルスとは異なり,地震観測と一致する亀裂のような破裂を生成することを明らかにします.
科学分野:
- 地理学
- 地震学
- 計算地質学
背景:
- 熟成した断層は,予測された静的強度よりも著しく低いストレスレベルで大きな地震を宿している.
- これを説明する主な仮説は,断層は準静的に強いが,動的に弱くなるか,断層は継続的に弱く,おそらく流体過圧によるものである.
研究 の 目的:
- 数値モデリングを用いて地震破裂ダイナミクスの競合する理論を調査する.
- 観測されたストレスの低下 (1-10 MPa) と限られた熱生成と一致する地震破裂をシミュレートする.
主な方法:
- 地震の破裂をシミュレートするために数値モデルを使用しました.
- 破裂の特徴を比較する (自己回復型のパルス型とクラック型)
- ストレスの変化 (静的対動的) と放射能を分析した.
主要な成果:
- ほぼ静的に強いが,動的に弱い断層は,高い動的ストレス変化で,鋭い,自己治癒のパルスのような断裂を生成します.
- 持続的に弱い断層は,比較可能な静的およびダイナミックなストレスの変化を持つより軽い,亀裂のような破裂を生成します.
- セルフヒーリングパルスは,メガスラストの観測よりもはるかに多くのエネルギーを放射しますが,亀裂のような破裂は観測と一致します.
結論:
- 弱い断層と亀裂のような断層は 巨大地震の地震学的な観測と一致しています
- 自己治癒パルスからの高い放射エネルギーは,メガスラストの設定では稀である,またはそのエネルギーは過小評価されていることを示します.
- 発見は地震の物理と地震の揺れに関する現在の理解に挑戦し,地質学的な設定の潜在的な違いを示唆しています.
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