We consider Isogeometric Analysis to simulate an earthquake in a two dimensional model of a sinusoidal shaped valley. We analyze two different time integration schemes, namely the Generalized- and the Leap-Frog methods. Solving a wave propagation problem leads to a numerical dispersion of the wave velocities which depends on the discrete function space, as well as on the direction of propagation. In this work we also analyze the numerical dispersion with respect to the number of quadrature nodes per wavelength and the direction of wave propagation.