We developed a three-dimensional computational model of the brain for studying harmonic deformations in the brain. Relevant substructures of the head are constructed from magnetic resonance imaging scans. Harmonic wave motions in a live human brain obtained in an MRE experiment were used to assess the accuracy of the computational model by comparing the measured and the predicted dynamic mechanical response of the brain. Quantitative comparison of strain field in simulations with measured data from MRE shows that the dynamic deformation of the brain tissue is responsive to changes in the viscoelastic properties of the brain. In addition, the results demonstrate the presence of falx membrane alters the spatial deformation field and peak strain amplitudes in the computational model of the brain. Furthermore, our model confirms a significant role of skull-brain interface in modulating dynamic deformations in the brain. Lastly, our model predicts large strains that could potentially induce brain injuries for frequencies of vibration higher than 10 KHz.