Because of the complexity of the dam failure mechanism due to earthquakes that occur under the simultaneous influence of hydraulic and seismic forces, a single model has not been obtained so far and this study was conducted to achieve this model. In this paper, dam failure models including both sudden and gradual failure have been investigated using volume of fluid techniques (VOF) to simulate water fluxes, general moving object (GMO) to simulate moving bodies, and the fluid–structure interaction model for finite volume analysis. In order to be sure of the accuracy of the results, before examining the failure mechanisms, the verifications of utilized methods in the case of dam failure were proven using experimental and numerical studies from literature. The Koyna Dam earthquake of magnitude 6.5 (11 December 1967) is investigated as a test case. Comparison of the output discharges due to dam failure in the two failure models reveals that the peak discharge of sudden failure is recorded three times faster than the gradual failure mode. Another achievement that should be mentioned is that although large oscillating periods carry a higher risk of cracking of the dam’s body, smaller periods propagate the resulting cracks more rapidly.