Ground topography effects on near-surface elastic full waveform inversion

The effects of neglecting ground surface topography variations in elastic full waveform inversion are investigated using two classes of synthetic example. The models include various high-contrast velocity and density anomalies, as they are often observed in near-surface applications. The first type of example shows that failing to account for even small amplitude fluctuations in topography introduces velocity artefacts in the near-surface part of the tomogram as well as degrades significantly the spatial resolution of features at greater depths. The disturbances are particularly severe when the topographic fluctuations have wavelengths comparable to the minimum seismic wavelength. The second type of synthetic example considers long wavelength topography variations of various amplitudes. It is found that neglecting topography with an amplitude fluctuation greater than half the minimum seismic wavelength leads to appreciable inversion image artefacts. Therefore, the incorporation of surface topography, even if it appears minor, is essential for successful elastic full waveform inversion of land seismic data.