Rockfalls seismic waves contain valuable information on event properties. However, as rockfalls predominately occur in mountainous regions, generated seismic waves are prone to be affected by strong surface topography. For this reason, the influence of topography on the wavefield, in particular surface wave propagation, is investigated using the Spectral Element Method on a 3D domain with realistic surface topography of Dolomieu crater on Piton de la Fournaise volcano, La Réunion. Topography induced ground motion modification is studied relative to a flat reference model. Peak Ground Velocity (PGV) and total kinetic energy can be (de-)amplified by factors up to 10 and 20, respectively. The spatial distribution of the amplification is strongly influenced by the underlying geology as shallow low velocities guide energy along the surface. Simulations on different topographies suggest that the wavefield is affected more by variations of crater curvature than crater depth. To reveal the effect of topography on recorded signals at Dolomieu crater, inter-station spectral ratios are computed. It is demonstrated that these ratios can only be simulated when taking into account surface topography while the comparisons suggest that the direction of the acting source and the resulting radiation patterns can be ignored. Finally, the seismic signature of single impacts is studied. Comparison with simulations help to associate signal pulses to impact sources. It is revealed that a single impact can provoke complex waveforms of multiple peaks, especially when considering topography. Impact forces derived from Hertz contact theory result in comparable magnitudes of real and simulated signal amplitudes.