地震 第2輯
Online ISSN : 1883-9029
Print ISSN : 0037-1114
ISSN-L : 0037-1114
伊豆諸島周辺における津波の規模
1990年2月20日大島近海津波・1990年9月24日東海道はるか沖津波
羽鳥 徳太郎
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ジャーナル フリー

1991 年 44 巻 4 号 p. 297-303

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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.

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