Purpose <p>The seismic behavior of concrete is best understood through nonlinear failure analysis, which is essential for accurately predicting potential failures. The study investigates the failure behavior of concrete gravity dams with long neck geometry under near and far field earthquakes, considering the Koyna dam as an illustrative example.</p> Methods <p>A nonlinear time history analysis is performed using the concrete damage plasticity (CDP) model to capture the material nonlinearity of concrete dams. The strain-based element deletion technique has been used for predicting the cracking behavior of the dams. The interaction effect of reservoir water is taken into consideration for the analysis. Three parametric case studies are performed by varying the water level, concrete grade, and silt layer addition to the bottom of the reservoir.</p> Results <p>The results are presented for three response parameters, namely, relative crest displacement, maximum, and minimum principal stresses. The variation of the responses is examined under different parametric conditions, including the effect of near-field fling step, near-field directivity, and far-field earthquakes.</p> Conclusion <p>The results from the analysis indicate that the dam is more vulnerable to near-field ground motions than the far-field ground motions. Furthermore, the change in the reservoir water level has resulted in the increase of 50% on the seismic behavior of the dams. The change in the grade of the concrete and addition of a silt layer have an impact as low as 15% on the seismic response of the dam.</p>