SEICHES WITH PERIODS OF SEVERAL HOURS OBSERVED IN MUTSU BAY AND SENDAI BAY

Abstract

 A survey has been carried out on characteristics of seiches with periods of several hours observed in Mutsu Bay and Sendai Bay. In Mutsu Bay, this seiche occurs throughout the year, but is particularly large in winter. The seasonal change in seiche amplitude variation correlates well with that in wind speed. Spectrum Analysis shows that there are two dominant periods around five hours. The seasonal changes of the energy of these two components are different. In Sendai Bay, seiche with about three hours develops when tidal deviation increases. The phases of vibration are well matched in Sendai, Ishinomaki and Ayukawa in Sendai Bay, but such seiches are not observed at points outside the bay. The amplification factor of the component with three hours is larger than other components when tidal deviation is large.