まとめ
膨張性仮説に基づくモデルは,地震前の低地震波速度比 (Vp/Vs) を説明する. 垂直またはランダムに指向した亀裂は,これらの影響を引き起こし,ブルー・マウンテン・レイクでも観察されています.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- 地震学 地震学とは
- 地震科学 地震科学 地震科学
背景:
- 異常に低い地震波の速度比 (圧縮波の速度と切断波の速度,Vp/Vs) は,地震の前に限られた地域で観測されています.
- 膨張性仮説は,岩石の裂け目形成と拡散が地震波の速度を変えることができることを示唆しています.
研究 の 目的:
- 地震前の観測された低いVp/Vs比を,膨張仮説を用いてモデル化し説明する.
- 異常ゾーンにおける地震波の伝播における亀裂の向きと密度の役割を調査する.
- ニューヨーク州ブルー・マウンテン・レイク (Blue Mountain Lake, New York) からの予兆観測でモデルを検証する.
主な方法:
- 地震波の伝播をシミュレートするために,膨張性仮説に基づく計算モデルを使用した.
- モデルの内部に様々なクラック・オリエンテーション (垂直,ランダム) と密度が組み込まれています.
- モデルの出力をソビエトの観測とブルーマウンテン湖の予備観測データと比較した.
主要な成果:
- モデルは,地震の前に観察された異常な低いVp/Vs比を成功裏に複製しました.
- 垂直の亀裂方向が観察された効果を生み出すのに最も効果的であることが判明したが,ランダムな亀裂のより高い密度は同様の結果をもたらした.
- モデルはまた,ニューヨークのブルー・マウンテン・レイク (Blue Mountain Lake, New York) からの予兆観測を複製した.
- 表面で測定されたVp/Vsは,異常ゾーンの境界特性に関連する転送関数によって影響されることを実証した.
結論:
- 拡張性仮説は,クラックメカニズムと組み合わせて,地震前のVp/Vs異常について,実行可能な説明を提供します.
- オリエンテッド・クラークによる地震アニソトロピーは,前駆的な地震観測において重要な役割を果たしている.
- Vp/Vsの表面測定は,地下構造と速度グラデーションの影響により,慎重に解釈する必要があります.
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