Seaquakes are generally considered the phenomena that a ship or a floating structure are shocked by the seismic waves which are propagated through the seawater. The effects of seaquakes on offshore floating structures are studied. Both effects concerning the compressibility of fluid and the free surface are discussed. The dynamic pressure acting on floating structures by seaquakes is investigated. The resonance is the important role of the effects of seaquakes on offshore floating structures. Numerically, boundary value problems are solved using the Green function method. After computations of the radiation hydrodynamic force and the vertical exciting force by seaquake, the frequency response of structure's heaving motions is evaluated.
In an effort to create much needed space, coastal developments such as the reclamation of shallow beach front areas and the creation of off shore artificial islands have been evolved in Japan. These developments are beneficial in areas where population density is concentrated and outward expansion is impractical due to surrounding mountainous terrain. The land reclamation has been the general policy to date. however a recent growing realization of the clear possible long term negative effects upon the coastal ocean environment of such land reclamation ion projects has given impetus to interest, in offshore floating structures. The Great Hanshin Earthquake of 1995 which struck the Kansai area encouraged this movement toward the development. of floating structures. In the artificial islands off Kobe. the massive earthquake caused the liquefaction of reclaimed lands and the quay wall built by the caisson method led to serious damage. However it. is important for floating pier structures to survive the earthquake with a significant lack of damage. Additionally, there are no reports that. any ships in Kobe bay area received by the earthquake. The lack of damage to ships is partly because the earthquake did not induce tsunami waves and seaquakes.
