This research investigates the effect of earthquakes on the Niayesh tunnel in Tehran Megacity. First, the amount of stress in the tunnel's up, wall, and bottom was calculated by analyzing the area's soil properties. Then, using the acceleration data from large earthquakes occurring in different directions of the tunnel construction, displacement and potential risk were assessed using PLAXIS software in three modes, static, quasi-static, and dynamic. These methods are used to calculate the deformation and displacement of the Niayesh tunnel. To determine the maximum displacement in three cases, the largest earthquake in the region should be considered. On average, this value was 45.6 mm at the earth's surface. The values obtained in the dynamic state show that surface ground movement in the tunnel restrains the area. The natural frequency of the Niayesh, calculated using Fourier spectrum analysis, is 5.94 Hz for the structure, which decreases to 5 Hz during an earthquake, with a corresponding period of 0.16 seconds and 2 seconds during an earthquake. In the static state, initial subsidence was obtained after the tunnel's construction. In dynamic mode, subsidence was calculated for three soil types modeled in Tehran Megacity by modeling the waveform of the Manjil earthquake. Results show that increasing the amount of soil elasticity during an earthquake enhances the acceleration created. Consequently, with the duration of the earthquake vibration and the increase in the earthquake's magnitude, the energy entering the tunnel increases with the release of seismic waves. The acceleration contour for the static and quasi-static methods was not plotted as it is time-independent, and the acceleration value is considered zero. However, in dynamic mode, the acceleration is time-dependent, and modeled accelerations applied to the structure over the considered period. If the acceleration ranges between 0.2 g and 0.5 g, mild and repairable injuries are expected, and from acceleration of more than 0.5 g, more severe injuries will be expected. According to the vertical displacement obtained using the static method in the Niayesh tunnel, the vertical displacement obtained was 24.5 mm, which was analyzed in three-dimensional mode. However, this study calculated the two-dimensional displacement value obtained as 22.48 mm. As a result, the tension created around the tunnel increases. A compressive state is created more than a tensile state. These results are inapplicable agreement with other results obtained in other underground spaces.