著者

羽鳥 徳太郎

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.44, no.4, pp.297-303, 1991-12-24 (Released:2010-03-11)

参考文献数

13

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Based on an epicentral distance dependence of tsunami amplitude observed at tide stations, the tsunami magnitudes were obtained to be m=-2 and m=-1 for the Oshima-Kinkai tsunami of Feb. 20, 1990 and the Tokaido-Oki tsunami of Sept. 24, 1990, respectively. The locality on magnitudes of the tsunamis generated along the Izu-Mariana Island-Arc since 1900 are discussed in relation to earthauake magnitude. According to the statistical relation, the magnitude values (Imamura-Iida scale) of the tsunamis generated near the trench triple junction off Boso Peninsula are one to two grades larger than the average tsunami magnitude. Such tsunamis were mostly caused by low-frequency earthquake with the high-angle dip-slip fault. While, the magnitudes of the tsunamis generated off the west side of Oshima Is. are one grade less than the average value, with caused by earthquakes of the strike-slip type. The magnitudes of a few tsunamis generated on the ridge were larger than the average value. Especially, the 1984 Torishima-Kinkai tsunami had an abnormal magnitude. The regional difference of seismic mechanisms were found by the deviation of tsunami magnitudes.