The effective numerical model that examines the seismic behavior of concrete gravity dams in the Laplace domain-Finite Element (FE) approach is presented. Further research on the potential damage levels and seismic performance of the dam body is done considering the simultaneous effect of horizontal (H) and vertical (V) components of six different earthquake loads. The time durations of the selected earthquakes vary from 10 sec to 80 sec with the magnitude range from 6.5 to 7.62 Mw. The Lagrangian fluid finite elements are utilized to model the near-field water domain. On the other hand, the fluid infinite elements are utilized to model the far-field water domain considering the rigid base rock foundation condition. The two-dimensional (2D) model is developed in FORTRAN 90 and MATLAB programming languages. The findings of this study suggest that the seismic behavior of concrete gravity dam affects not only with the seismic severity; the length and significant time duration of the earthquake are also important factor. The evaluation of the obtained results revealed that the longer length of significant earthquake duration leads to the high deformations, the high stress excursions and high probability of damages in the dam. 20.9% and 18.8% of the selected dam cross section experiences overstress condition under the H and H + V components of the Chi-Chi earthquake loads, respectively; which result the dam failure.