For the Tonankai earthquake of 1944, somewhat different fault models have been proposed by Kanamori (Model I), Ando (Model II), Inouchi and Sato (Model III), and Ishibashi (Model IV). These fault models are examined, in the present paper, from the view-point of the tsunami generation and the optimum model with respect to the tsunami is selected. At first the tsunami behavior originated from each fault model are computed with the aid of hydrodynamic numerical experiments. Then, the geographic distribution of ratios of the observed to the computed wave amplitudes for the first and the second half cycles at 6 tidegage stations extending over 700 km along the Pacific coast of Honshu and Shikoku are examined. If these ratios do not depend on the locations, then the fault model may be considered to be consistent with the observed tsunami behavior, provided that the magnitude of the fault slip is to be multiplied by the mean value of the ratios. By these procedures, it is found that Model IIP by Inouchi and Sato with the reducing facter 0.45 seems to be the best among the four models. In this model, two fault planes are assumed to strike in the direction of N45°E from the point of 33.08°N and 136.3°E. The first fault has the area of 154 km long and 67 km wide and the second fault the area of 84 km long and 78 km wide on the northeastern extension of the first fault. The slip displacements of both faults are given as 2.0 m and 1.4 m for the reversal dip-slip component and 0.7 m and 0.5 m for the left lateral component, respectively. The Model III'with the above reduction gives reasonable ratios between the computed wave height along the 200 m depth contour and the measured run-up heights along the coast line of 360 km facing directly the tsunami source area. Furthermore, by the detailed computations within the bays, the satisfactory agreement of the observed and the computed wave patterns is achieved at Owase bay which is located near the center of tsunami source and in Shimoda bay which is about 150 km distant from the margin of the source area. In conclusion, a seismic fault model can be considered a fairly good approximation to the source model for the tsunami generated in the region along the Nankai trough.

雑誌名

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo

巻

54

号

2

ページ

329 - 341

発行年

1979-12-25

ISSN

00408972

書誌レコードID

AN00162258

フォーマット

application/pdf

日本十進分類法

453

出版者

東京大学地震研究所

出版者別名

Earthquake Research Institute, University of Tokyo

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