No abstract

The differences between onshore and offshore ground motions were studied based on the records from the K-net and SEMS. The horizontal response spectrum and vertical-to-horizontal response spectral ratio for offshore and adjacent onshore ground motions were analyzed. The results indicate that the characteristic period of the response spectra for offshore ground motions is obviously larger. The epicentral distance can influence the horizontal response spectra for offshore ground motions in a moderate earthquake, while the influence of water depth is not noticeable. Moreover, the vertical-to-horizontal response spectral ratio for offshore ground motions is significantly smaller for periods less than 1 s.

A simulation method of spatially correlated seafloor motions is proposed by considering the influences of seawater on the seafloor motions and their spatial variations at different subsea sites. The offshore site transfer functions are theoretically derived using the fundamental hydrodynamics and one-dimensional wave propagation theory. Three-dimensional spatially varying ground motions on the surfaces of multiple onshore and offshore sites are synthesized based on the spectral representation method and the calculated site transfer functions. A pair of onshore and seafloor recordings from the same earthquake event is employed to examine the basic characteristics of simulated onshore and seafloor motions.

No abstract

No abstract