ブレーク・グラウンド:地震がなぜ起こるのか、幾何学が新たな説明をしてくれるのだろうか?(Breaking ground: Could geometry offer a new explanation for why earthquakes happen?)

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2024-06-05 ブラウン大学

ブラウン大学の研究者たちは、地震が発生する際の断層の幾何学的構造を詳しく調べ、地震発生の新たな要因を明らかにしました。研究は、断層ネットワークの配置が地震の発生場所と強度を決定する重要な役割を果たすことを示し、従来の摩擦特性が主な要因であるとする見解に挑戦しています。カリフォルニアの断層データを用いた研究では、幾何学的に複雑な断層ゾーンが強い地震を引き起こし、単純なゾーンは滑らかに滑るだけで地震を引き起こさないことが示されました。この発見は、将来的に地震予測モデルに組み込まれる可能性があります。

<関連情報>

断層網の形状が地震の摩擦挙動に影響する Fault-network geometry influences earthquake frictional behaviour

Jaeseok Lee,Victor C. Tsai,Greg Hirth,Avigyan Chatterjee & Daniel T. Trugman
Nature  Published:05 June 2024
DOI:https://doi.org/10.1038/s41586-024-07518-6

ブレーク・グラウンド:地震がなぜ起こるのか、幾何学が新たな説明をしてくれるのだろうか?(Breaking ground: Could geometry offer a new explanation for why earthquakes happen?)

Abstract

Understanding the factors governing the stability of fault slip is a crucial problem in fault mechanics1,2,3. The importance of fault geometry and roughness on fault-slip behaviour has been highlighted in recent lab experiments4,5,6,7 and numerical models8,9,10,11, and emerging evidence suggests that large-scale complexities in fault networks have a vital role in the fault-rupture process12,13,14,15,16,17,18. Here we present a new perspective on fault creep by investigating the link between fault-network geometry and surface creep rates in California, USA. Our analysis reveals that fault groups exhibiting creeping behaviour show smaller misalignment in their fault-network geometry. The observation indicates that the surface fault traces of creeping regions tend to be simple, whereas locked regions tend to be more complex. We propose that the presence of complex fault-network geometries results in geometric locking that promotes stick-slip behaviour characterized by earthquakes, whereas simpler geometries facilitate smooth fault creep. Our findings challenge traditional hypotheses on the physical origins of fault creep explained primarily in terms of fault friction19,20,21 and demonstrate the potential for a new framework in which large-scale earthquake frictional behaviour is determined by a combination of geometric factors and rheological yielding properties.

1702地球物理及び地球化学
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