超巨大地震発生前後の顕著な地震活動

• 小山 順二

  北海道大学大学院理学研究院自然史科学部門

• 都筑 基博

  北海道大学大学院理学研究院自然史科学部門

書誌事項

タイトル別名

• Activity of Significant Earthquakes before and after Megathrust Earthquakes in the World

抄録

After the 2011 Tohoku-oki megathrust earthquake of M_w 9.0, we observed tens of thousands of inland and volcanic earthquakes all over the Japan Islands, which are not confined within the aftershock area of off the Pacific coast of Tohoku region. This reminds us to evaluate the earthquake activity in a much wider sense, discarding an ordinary idea of the foreshock-mainshock-aftershock activity within a limited aftershock area of a particular earthquake. There occurred several megathrust earthquakes worldwide in the last one hundred years. We have studied their significant events before and after the earthquakes based on our new hypothesis on the earthquake generating zone with the distinct difference between Along-dip Double Segmentation (ADDS) and Along-strike Single Segmentation (ASSS). In summary, some of significant aftershocks (larger than M_w 7.5) of ADDS megathrusts are those (Type I) in and near outer-rises, where some are dip-slip normal faultings and some are strike-slip faultings within subducting oceanic plates with component of normal fault. These outer-rise earthquakes are considered to be controlled by the slab-pull of descending slabs of oceanic plates induced by the reduction of plate couplings by megathrusts. In addition, some are also significant (Type II) along the plate interfaces within aftershock areas and those extending aftershock areas similarly to the corresponding megathrusts. On the other hand, aftershocks of ASSS occurred in and near corresponding aftershock areas and significant and or disastrous outer-rise events are rare. Some large (not significant) inland earthquakes are also known for both ADDS and ASSS megathrusts. All these results are not dependent on whether the subduction geometry is oblique or orthogonal.

収録刊行物

• 地震　第２輯

  地震　第２輯 66 (4), 83-95, 2014

  公益社団法人 日本地震学会

キーワード

• Megathrust earthquake
• Along-dip Double Segmentaion
• Along-strike Single Segmentation
• Significant aftershock
• Outer-rise earthquake

詳細情報

• CRID: 1390001204304270592
• NII論文ID: 130004562113
• DOI: 10.4294/zisin.66.83
• ISSN: 18839029
• ISSN: 2186599X
• ISSN: 00371114
• 本文言語コード: ja
• データソース種別:
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