Temporal features of the aftershock activities following some large shallow earthquakes of M>7 in Japan have been studied quantitatively. The earthquakes concerned were accompanied by large aftershocks which triggered their own aftershock activities. The purpose of the present study is to seek any anomalous change in aftershock activities of the main shock before the occurrence of such large aftershocks. Aftershock activity shows an appreciable decrease from the level expected from the modified Omori formula before the occurrence of a large aftershock. The aftershock activity then recovers to the normal level or evev increases beyond the normal level shortly before the occurrence of the large aftershock. The recovered activity generally occurs near the hypocenter of the forthcoming large aftershock. Such a feature has been recognized in fourteen cases out of eighteen for which sufficient data are available. We have the possibility of predicting the occurrence of a large aftershock which might be as large and disastrous as the main shock, if we keep watch on the change of the aftershock activity immediately following the main shock. Moreover, a rough prediction of the place can be made by checking the hypocenter location of aftershocks occuring in the recovered stage.
雑誌名
東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo
巻
61
号
1
ページ
1 - 65
発行年
1986-08-04
ISSN
00408972
書誌レコードID
AN00162258
フォーマット
application/pdf
日本十進分類法
453
出版者
東京大学地震研究所
出版者別名
Earthquake Research Institute, University of Tokyo
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Precursory Quiescence and Recovery of Aftershock Activities before Some Large Aftershocks
ji0611001.pdf
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