Finite difference 2D elastic modeling is used to study characteristics of the wave field originated by the near surface and the topography. A number of geological models, from flat horizontal to a real topography from a rough setting are presented and results of variation in velocities and waveforms are compared for a number of cases with and without a near surface low velocity layer. It can b noticed that many coherent noise events are generated in the low velocity near surface layer. Many of them resemble real data seismograms. Some of them are rarely observed in real data and could be related to the characteristics of the algorithm or perhaps to unrealistic velocity models. The surface waves appear dispersive and/or weaker in the presence of topography. Converted waves appear distorted and difficult to identify on some seismograms, mostly due to this coherent noise. The real topography model shows noisy events not clearly defined, which can be related to the dispersion caused by the topography.
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