When a major earthquake occurs, it can be followed by an incoming tsunami, both of which destroy many structures and cause serious damage. Although the destruction of structures caused by earthquakes and by tsunamis has been studied, the further damage caused by aftershocks after a major earthquake occurring at the time of a tsunami has not been sufficiently reported. In this study, we aimed to determine variations in the influence of different structural shapes when the effects of an earthquake and tsunami are superposed. A sloping structure was shown to reduce the hydrodynamic pressure; even when an earthquake and tsunami occur simultaneously.