Abstract
In the previous paper under the same title, the results of model experiment by Mr. Matuo concerning the tunami in the Osaka Bay was compared with results calculated from hydrodynamical theory. but it scarcely succeeded in bringing both in good agreement.
In this paper the amplitude and time of occurrence of lst wave are newly measured from the records of model expriment (Fig. 1), and it is tried again to explain them theoretically.
The observed travel time is in good agreement with what calculated as velocity is √gS/b, where S, b are the sectional area and the breadth of the Bay respectively. We regard the tunami as a long wave and put for its hydrodynamical equation under the influence of frictional force and put (that is velocity) then for f we have From this equation f is evaluated by numerical integration (table 1) adopting the observed values β given in Table 2. The results follows the observed curve closely enough (Fig.3).
The values of B(=βT/2π) (table2) for the model experiment are very large and it is not considered to be the case in the nature. The β for the tunami which occurred in the Tokyo Bay at the great Kwanto earthquake in 1923 is evaluated from the then mareogram at Yokosuka (Table 4). We see that it is very small compared with that of Table 3. The f for the tunami in the Osaka Bay under this value β is calculated by numerical integration by the equation (1). The results are illustrated in Fig. 5 in which the mode of dissipation for the wave energy are also shown.
