Abstract
The seiche obtained from tide gauge data in the Aburatsubo Tide Station has the period of 13.5-15.5 minutes and the amplitude of 85 mm. In order to confirm the Seiche theoretically, the author applies a Y-shaped one-dimensional model to Aburatsubo and Moroiso bays. The result shows that the free oscillation of sea-surface has the periods of 12.93, 7.18 and 4.82 minutes, respectively, corresponding to the fundamental, the second and the third harmonic waves, although the existence of higher harmonics is not confirmed from the observation. It is proved that the node of the second harmonic is near the tiltmeter station, and Koajiro bay seems ineffective on the seiche in Aburatsubo bay. Tiltmeter observations indicate that the effects of the seiche have E-W and N-S tilt components amounting to 2.35×10-3 and 9.43×10-3 second of arc, respectively. On the other hand, the tilting amplitudes by the seiche are theoretically estimated to be 2.95×10-3 and 3.21×10-3 second of arc, respectively. The calculated result shows a good coincidence with the E-W component observed but it becomes about a third of the observed value for the N-S component.
