3D P-wave synthetic seismograms in several 2D isotropic heterogeneous models have been computed using the first-order ray-based Born approximation and the ray theory. The Born approximation is computed in a 2D grid, and the background model is a 2D smooth heterogeneous isotropic velocity model. The seismograms have been computed for the total number of 37 receivers. The strange wavegroups are observed in the Born seismograms. The explanation is that these problems are caused by caustics on the direct wave. Three solutions are proposed. Seismograms corrected using one of these solutions are shown. Furthermore, particular wavegroups present in the Born seismograms and missing in the ray-theory seismograms are discussed.
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