200m等深線上の津波波形と浸水高

抄録

Reliability of the tsunami source model inferred from the dislocation theory of faulting was approximately verified previously, comparing the result of a numerical experiment with tsunami records at the coast. On the basis of above results, water surface profiles on a 200m depth contour have been computed numerically by use of the tsunami source model obtained from the fault parameters of the Tokachi-oki earthquakes of 1968 and 1952. Computed water elevation-time histories indicate the significant character for the directivity of the wave radiation from the source, that is the sense of rise or fall in the leading wave and the wave period. The wave heights (H₀), of source, vary depending on locations on a 200m depth contour. Tsunami inundation heights (R) at a coast and H₀ are plotted along the Pacific coast of the Tohoku and Hokkaido districts. Then, average inundation heights (R_avg), which are used instead of R rather scattered, are fairly well parallel to H₀ and R_avg/H₀=2-3. It is recognised by a simple calculation that the values of R_avg/H₀ are reasonable as the amplification factor of water oscillations on a continental shelf. Therefore, the tsunami source model based on the dislocation theory of faulting seems to give results fairly consistent with the major character of tsunami, at least, in the Pacific coast of Tohoku district. Thus the kind of a numerical experiment may be a usefull method for a prediction of tsunami inundation at the coast of interest.