The phenomenon of large-area rockmass failure has been observed in Daliushu dam site on the Yellow River. In order to study the failure mechanism of this rockmass

the intrinsic relationship between dynamic effect of earthquake and rockmass dynamic failure is put forward on the basis of detailed investigations of regional geological environments and regional seismic dynamics; and dynamic simulation experiment are conducted on the failure phenomenon. The experimental results show that the large-area rockmass dynamic failure in Daliushu dam site area is closely related to the meizoseism history. Consequently

the dam site would be damaged more seriously once the seismic activity of the same scale happens.