Abstract
Peculiar tsunami waves p roduced by the eruption of a submarine volcano at Myojinsho Reef on March 11,1953 were recorded by wave gauges installed on Hachijojima Island, Cape Ornaezaki and Jogashima Island, which are distant from the volcano by 130,336 and 356 km, respectively. Moreover, from the 11th to the 25th of March tsunami waves were recorded about fifty times at Hachijojima Island. From these data we could make clear the features of the variation of waves with distance as well as with time, and it was proved that the theory of Cauchy-Poisson wave explains these waves satisfactorily. It was also shown that these waves were caused by an initial impulse rather than by an initial elevation at the moment of explosion, and that the waves progressed with group velocjty. In order to understand two kinds of tsunami waves, one of which shows a conspicuous beat phenomenon while the other does not, discussions were made on the effect of initial impulse of different types.
