Effects of seismic wave inputting interface on designed surface ground motion in AP1000 nuclear island structure

In the process of seismic hazard assessment of nuclear power plant, there are some differences on bedrock faces that were defined according to shear wave velocity between China and America code. We select different bedrock faces, based on AP1000 Nuclear Power Plant design ground parameter model, that corresponding to Shear wave velocity of 700 m/s, 1100 m/s and 2438 m/s, and using two methods of Chinese and American seismic responses for soil lays, we analyze the different seismic input. interface on one analysis model and one seismic input, and obtain the peak acceleration of ground motion and response spectrum. The calculation results indicate that different seismic interface in one soil model and one seismic input could result in quite different results, and AP1000 Nuclear Power Plant design surface ground motion and spectrum characteristics change greatly, and the difference of peak acceleration of ground motion can be 2.25 times. So we suggest that we should use shear wave velocity of 2438 m/s as the seismic input interface in AP1000 nuclear power plant site seismic safety analysis. The results of the paper could give some guidance for the later AP1000 Nuclear Power Plant construction and research. (authors)