地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
津波波形から推定された1944年東南海地震及び1946年南海地震のすべり量分布の解釈
谷岡 勇市郎
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ジャーナル フリー

2001 年 110 巻 4 号 p. 491-497

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The slip distributions of the 1944 Tonankai earthquake (Tanioka and Satake, 2001b) and the 1946 Nankai earthquake (Tanioka and Satake, 2001a) estimated using tsunami waveforms were reviewed. In the source region off Kii peninsula, the large slip extended over the entire locked zone. However, in the source region off Shikoku, Shima peninsula or Atsumi peninsula, the slip on the up-dip or shallow part was limited. Parts of these may be explained by the existence of splay fault (up-dip subfault) systems in the accretionally prism. The tsunami waves from those earthquakes were observed not only at tide gauges in Japan, but also at Honolulu, Hawaii. The tsunami at Honolulu from the 1946 Nankai earthquake was smaller than that from the 1944 Tonankai earthquake, although the seismic moment of the 1946 Nankai earthquake is much larger than the 1944 Tonankai earthquake. The numerical tsunami computation was carried out for the 1944 and 1946 events. The largest slip region near Shikoku for the 1946 Nankai earthquake was close to the shore, so the large parts of tsunami energy were trapped in the shallow sea and were not transmitted into the deep ocean. That is one of the reasons why the tsunami observed at Honolulu from the 1944 event was larger than that of the 1946 event.

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