The earthquake input model is fundamental in seismic responses analysis of a gravity dam. This paper first presents a theoretical analysis on the characteristics of motion fields that are expressed by four earthquake input models

then uses a random wavefield method to quantify incident waves and the corresponding ground motions

which ensures the unified input criterion shared by different earthquake input models. Finally

we simulate the seismic responses of a gravity dam using different earthquake input models

and offer a quantitative demonstration of the radiation-damping effect and complicated wavefield effect. The dam responses calculated using different earthquake input models are similar in trends

but their magnitudes are considerably different. For peak σ1 at the dam heel

the responses vary in the range of -68.2% to -14.8% caused by the radiation-damping effect

and -8.7% to 53.0% by the complex wavefield effect. This study reveals the influence of the complex wavefield effect

promoting the development of seismic response analysis of gravity dams.