We present a detailed approach to implement a moment-tensor point source to compute displacements, particle velocities and accelerations using direct grid methods. Here, the wave modeling algorithm is based on pseudospectral methods to compute the partial derivatives. A comparison to the analytical solution in the 3D acoustic case verifies the discrete implementation of the source in the mesh. Then, the more general 3D elastic case is illustrated and simulations, with and without free surface,

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... re performed that can be used as a reference solution for other grid methods.