The paper pertains to the seismic analysis of earth and rockfill dams with the aid of MSC_ Nastran (Windows) package. After validation, the package has been used to investigate the dynamic response of Tehri Dam, located in the seismically active region of Himalayas. A 2D FEM analysis is adopted wherein the dam has been modeled as a linear, elastic, non-homogeneous material. The base acceleration data of the Bhuj Earthquake has been used as an input motion. Effect of Poisson’s ratio and the ratio of the canyon length to the height of the dam has been investigated and is reported. Acceleration-time histories reveal that the maximum acceleration occurs at the crest of the dam, and decreases towards the bottom of the dam. Displacement-time histories reveal that the vertical displacement at any locations of the dam is negligibly small compared to the horizontal displacement. The shear stresses evaluated displays a maximum and minimum magnitude at the shell and core of the dam respectively. Velocity-time history shows a maximum velocity in the forward direction at the crest of the dam, while in the reverse direction, the same is experienced by the shell and the core of the dam supplemented by a noticeable phase difference
