著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.57, no.3, pp.525-535, 1983-01-17

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A small tsunami was generated by the Urakawa-oki earthquake (M=7.1) near Cape Erimo, southern Hokkaido, on March 21, 1982. At Urakawa, the initial disturbance of the present tsunami began with an upward motion simultaneous with the earthquake occurrence. The first wave period was 16min and the third wave was the highest with a semi-amplitude of 80 cm. According to the author's method based on the attenuation of wave-amplitude with distance, the tsunami magnitude (Imamura-Iida scale) are estimated to be m = 0. This rank is average for an earthquake having a magnitude of M=7.1. The source area of the present tsunami which inferred from an inverse refraction diagram is located along the coast from Urakawa to Shizunai. The length of the tsunami source is 40 km and the width 20 km. The tsunami source area agrees with the aftershock area. From the analysis of the initial tsunami motion on the records, an average uplift of 14 cm may have occurred at the sea-bottom of the source area.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.59, no.1, pp.p115-125, 1984

被引用文献数

3

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新史料を加え,1741年渡島沖津波の波高を再検討した.また,北海道渡島沿岸を現地調査し,熊石にある津波地蔵・過去帳を紹介した.津波の高さは渡島沿岸で10m,局地的には15mに達し,津軽で5~6m,佐渡では4~5mと推定される.津波マグニチュードは,Δ-Hグラフからm=3.5と見積もれる.波高分布のピークは1983年日本海中部津波のものより北側に片寄り,波源域は渡島半島沖の水深3,000mの海域を中心に,長さ150kmの範囲にあったと考える.Adding new data on the Oshima tsunami of Aug. 29, 1741, the inundation heights along the coast of the Japan Sea are reexamined. About 2,000 persons drowned at 22 villages within the 90 km stretch (Matsumae to Kumaishi) along the west coast of Oshima Peninsula, West Hokkaido. A religious monument and an old document were newly found at a temple in Kumaishi. Considering ground level, inundation heights (above sea level) of the tsunami along the Oshima coast were estimated to be 10m with local run-ups as much as 15m. The estimated inundation heights are 5-6m at Tsugaru (Aomori Pre.), 3-4m at Noto-Shitsura (Ishikawa Pre.), 1m at Obama (Fukui Pre.) and 1-2m at Gotsu (Shimane Pre.). The distribution pattern of the heights on Sado Island is highly similar to that of the 1983 NihonkaiChubu tsunami. However, the wave-period of the 1741 Oshima tsunami is longer than that of the 1983 tsunami, because the wave-heights are large in the big bays at Aburakawa and Ryotsu. Judging from the attenuation of tsunami height (semi-amplitude) with distance, the tsunami magnitude (Imamura-Iida scale) is m=3.5. The tsunami energy is five time larger than that of the 1983 tsunami (m=2.5). Compared to the magnitude and the distribution pattern of heights for the 1983 tsunami, this suggests that the source area of the 1741 tsunami extends about 150km along the bathymetric line 3,000m off the Oshima Peninsula.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.51, no.2, pp.p63-81, 1976-12

被引用文献数

1

著者

羽鳥 徳太郎 相田 勇 岩崎 伸一 日比谷 紀之

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.56, no.1, pp.p245-263, 1981

被引用文献数

1

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Owase located on the east side of Kii Peninsula has been hit by many tsunamis. Sources of most tsunamis were off Tokaido along the Nankai Trough. The 1960 Chile tsunami that propagated across the Pacific Ocean also hit Owase City. There remain even now traces of the inundated level on many houses in Owase caused by the 1944 Tonankai and 1960 Chile tsunamis. Based on these traces, the inundation heights of the two tsunamis run-up on land were surveyed, using the automatic level from Nov. 4 to 7, 1980. The relation between the geographical distribution of the inundation heights and the damage to houses was investigated. The results of the present surveys are as follows: 1) The inundation heights of the 1944 Tonankai tsunami at the harbor were 5.0-5.5 m above M.S.L. Ground about 3.0 m above M.S.L. was inundated. The inundated area stretched along the Kita River. The water level decreased in height as it moved inland. The topography of the ground controls the damage to houses. Fifty percent of the ordinary Japanese wooden type houses were damaged when the water reached 1.5 m above the ground. From the inclination of the water surface along the Kita River, the mean water velocity is calculated as 3.5 m/sec. 2) The inundation heights of the 1960 Chile tsunami at the harbor were 3.0-3.5 m above M.S.L. Although the water reached 1.0-1.5 m above the ground, hardly any houses were washed away. The traces of the inundated level into land are nearly flat, suggesting that the velocity of the incident flow was small. 3) Based on old documents, the inundation height of the Ansei Tokai tsunami (Dec. 23, 1854) is estimated as 6.5 m above M. S. L. The heignt is 0.7-1 m higher than that of the 1944 Tonankai tsunami. Ground above 4 m high was inundated.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.54, no.2, pp.343-350, 1979-12-25

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The Oshima tsunami of Aug. 29, 1741 (Kampo 1) is the largest tsunami (Imamura-Iida scale m=3) generated in the Japan Sea. According to old documents, the wide area (length 500 km) from west Hokkaido, Tsugaru to Sado Is. suffered severe damage by this tsunami. 1,467 persons were drowned at various villages within 120 km (Matsumae to Kumaishi) along the west coast of the Oshima Peninsula. In the temples of Matsumae and Esashi, there are old monuments which were built just after the tsunami to pray for the repose of the tsunami victims. From the present field investigation, these tsunami monuments are illustrated. Considering ground level, inundation heights of the tsunami along the west coast of the Oshima Peninsula seem to have reached 6 to 8 m with the localized run-up maximum of about 15 meters. The eruptions of the Oshima volcano began 11 days before the tsunami generation and the volcanic activity continued for three months, but earthquakes were not recorded. Judging from the tsunami magnitude and the distribution pattern of wave-heights, it seems that the source area of tsunami extends 100 km or more along a bathymetric line of 3,000 m off the Oshima Peninsula.