Frequency-domain wavefield differences and conversion between 2.5D and 2D seismic wave modelling in elastic anisotropic media

We applied our newly-developed frequency-domain seismic wave modelling technique - the Gaussian Quadrature Grid (GQG) method - to distinguish between the line-source (2D) and point-source (2.5D) seismic wavefields in 2D elastic anisotropic media. Simple asymptotic filters are often employed to convert field data from point source to line source to enable efficient 2D elastic wave migration and full-waveform inversion to be applied. We employ various elastic anisotropic media with arbitrary free-surface topography to investigate the differences between 2D and 2.5D full-waveform spectral data. Our results indicate that after application of the simple filters to the 2.5D wavefields, there are still significant mismatches between the converted 2.5D data and the true 2D wavefields in these media. A stretching factor, given by the ratio of the sum of the absolute value between the 2D and converted 2.5D data, is proposed for further correction. Despite small errors, the converted and stretched 2.5D data have approximately the same amplitude and phase as the true 2D data, which suggests that this simple process may be utilized for transforming point source field data for effective and efficient imaging of 2D structures using 2D migration and full-waveform inversion algorithms when the geology is truly 2D.