ランダーとヘクター鉱山の地震の後,地震波によって引き起こされた地震

J Gomberg¹, P A Reasenberg, P Bodin

¹US Geological Survey, Center for Earthquake Research and Information, 3876 Central Avenue Suite 2, Memphis, Tennessee 38152-3050, USA. gomberg@usgs.gov

Nature

|May 25, 2001

まとめ

大規模な地震からの一時的な地震波は余震を引き起こす可能性があります. 動的ストレスの変化は,静的な変化を超えて,この地震誘発現象,特により大きな距離での重要な役割を果たします.

科学分野:

地震地震学地震学
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:

1992年のランダーズ地震と1999年のヘクター鉱山地震は,地震の誘発を研究するためのユニークな機会を提供します.
以前の研究では,地震波によるダイナミックな変形が地震率を増加させることが示唆されていた.

研究の目的:

ランダーズ鉱山とヘクター鉱山の地震後の地震率の変化の空間的および時間的なパターンを定量化するために.
地震の誘発における動的および静的なストレス変化の役割を調査する.
ダイナミックなトリガリングの値と,その局所条件との関係を決定する.

主な方法:

ランダーズ鉱山とヘクター鉱山の地震に対応した地震率の変化の分析.
観測された地震性のパターンと地震波の伝播とストレス変化モデルの比較.
ダイナミックトリガリングの値を推論するためにピーク地震速度の定量化.

主要な成果:

ランダースの北とヘクター鉱山の南に地震発生率の増加が観測され,破裂方向性と一致しています.
動的および静的ストレスの変化の両方がトリガーに寄与し,動的ストレスがより大きな距離で支配する.
動的トリガー値は,10分の1から数MPaの範囲で,静的値よりも大幅に高いと推定されました.
動的変形が緩んだ後,いくつかのサイトで遅延誘発が観察されました.

結論:

地震波として放射されるダイナミックな変形は,地震を誘発する重要な要因です.
破裂方向性は,動的ストレスとそれに続く地震性の空間的分布に影響します.
この発見は,地震の誘発における液化や周期的疲労のような物理的メカニズムを裏付けている.

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