著者

吉田 明夫 高山 博之

出版者

Tokyo Geographical Society

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.103, no.6, pp.696-705, 1994-12-10

参考文献数

12

被引用文献数

1 1

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We show that seismic activity decreased clearly in a wide area before the 1953 Boso-oki earthquake and the 1972 Hechijojima-toho-oki earthquake. In both cases the seismic quiescence extended to the Tokyo Metropolitan area. Marking precursory activity appeared several years before the Boso-oki earthquake in the Chiba prefecture and in the sea region off-Ibaraki prefecture. It is also noted that the seismicity in the Kanto region as well as in the sea region south off-Boso Peninsula decreased conspicuously after the Boso-oki earthquake. On the contrary an increase of the seismicity was observed after the Hachijojima-toho-oki earthquake, although deep seismic activities decreased remarkably. We show that seismic quiescences preceding the Boso-oki earthquake and the Hachijojima-toho-oki earthquake were detectable before their occurrences, and no other statistically significant quiescence has appeared in the south off-Kanto region since 1926. It is proposed that the occurrence of a large earthquake may be predicted by monitoring changes of the seismicity in a wide area.