著者

渡辺 偉夫

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.50, no.1, pp.29-36, 1997-05-28 (Released:2010-03-11)

参考文献数

20

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A method for judging tsunami earthquake is proposed. The method uses a simple formula for calculating the judging factor α from JMA seismic intensity and epicentral distance. α corresponds to the difference between the tsunami magnitude by WATANABE (1995) Mto and JMA earthquake magnitude MJ. [WATANABE (1994)]We apply this method to some recent and some historical tsunamigenic earthquakes around the Japan Islands. The results are as follows.1) Among 19 tsunami earthquakes, eight earthquakes have α values of 0.6 or more and one has α value of 0.5.2) The criterion α≥0.6 is suitable for identifying tsunami earthquake, because number of tsunami earthquakes of α≥0.6 is almost the same as the number of earthquakes of Mto-MJ≥0.6.3) Historical earthquakes of 1605, 1611 and 1677 were tsunami earthquakes. However, the earthquake of 1793 had a normal tsunami.4) Tsunami earthquakes around the Japan Islands are distributed along the Japan trench, off the southeast coast of Hokkaido and along the Nankai trough. It must be noticed that two tsunami earthquakes of 1611 and 1896 occurred off the Sanriku coast, and the two tsunami earthquakes occurred simultaneously in 1605 off the Kii peninsula and the Tokai coast.