Seismic response of a composite breakwater 60 m deep has been recorded, including accelerations and hydro dynamic pressures during earthquakes. The maximum accelerations at the base are less than 100 Gals and, thus, this report constitutes an interim report. The following tentative conclusions are obtained.
(1)Frequency response of the composite breakwater consists of a predominant frequency of 1.6 Hz for a rubble mound-caisson system and 2.2 Hz for a caisson, both of which predominate in the seismic response at the top of the caisson.
(2)Maximum hydro dynamic pressures measured during earthquakes are equal to or smaller than those computed based on Westergaard's and Zanger's formulae.
(3)Maximum accelerations and hydrodynamic pressures computed based on equivalent linear analysis are consistent with those measured. This indicates the applicability of the equivalent linear analysis for seismic response of a composite breakwater 60 m deep during earthquakes up to 100 Gals.