10. On the Tsunami which accompanied the Earthqtiake off the Northwest of Oga on May 7, 1964

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The tsunami, which was generated off the northwest of Oga Peninsula in Akita Prefecture, at 16 h 58m 7.7s(JST), May 7, 1964, was observed at many tide-gauge stations along the coast of the Japan Sea. The heights of tsunami were small. The epicenter of the earthquake was at 40°20'N, 139°00'E, with a depth of Okm and magnitude 6.9. The generating area of tsunami, which was extended 50～70km was estimated by means of an inverse refraction diagram from eight tide-gauge stations. At all the stations inspected, the initial motion of the tsunami was found to be directed upwards, showing that the crustal deformation which caused the tsunami was probably an upheaval in the source area. Generally speaking, the upheaval seems to have been small but somewhat conspicuous in the northeastern part of the tsunami source area.昭和39年5月7日16時58分7.7秒,男鹿半島仲に発生した地震で,(気象庁によれば,40°20'N,139°00'E,h=0km,M=6.9)秋田県八郎潟干拓地域に可成りの被害を与えた.この地震に伴ない軽微な津波が発生し,北沿道南西部,東北地方西部沿岸における最高波高(全振幅)分布はFig.1のようになり,昭和14年5月1日男鹿地震の津波とほぼ同程度の規模である.従つて今回の津波は検潮流で計測し得る程度の大きさのため,現地調査を行わず各地から収集した13箇所の検潮記録について検討した.
1965-07-15