Abstract
After 45 minutes of the commencement of the great earthquake, our tide guage installed at the beach near this observatory traced an ascent of about 15cm which was succeeding by a descent of 24cm. of the sea level. The interval of time between the maximum and minimum of the height of the level was about 10 minutes. Such an oscilation of the level was then repeated a few times, meanwhile the average level was sinking gradually, and at last at 1h 19m pm. the lowest level was reached whose depth was 81cm. above the zero of the guage with an oscilation of the ascent of 49cm and a descent of 33cm. This was the one with the maximum amplitude and succeeded by complex oscilations for 3 hours. Along the coast from Sunosaki to Nozimasaki the intensity of Tsunami was greatest of these districts.
Since January this year (1923) the water-stand of the ocean observed in this observatory was gradually rising. In May, June and July the average stand was higher than that in the last year by 18cm. In August the difference increased to 24cm and before the great earthquake it amounted to about 30cm. which was proved to have been maintained after the said phenomenon.
