Abstract
Multiparameter full waveform inversion (FWI) applied to an elastic orthorhombic model description of the subsurface requires in theory a nine-parameter representation of each pixel of the model. Even with optimal acquisition on the Earth surface that includes large offsets, full azimuth, and multicomponent sensors, the potential for trade-off between the elastic orthorhombic parameters are large. The first step to understanding such trade-off is analysing the scattering potential of each parameter, and specifically, its scattering radiation patterns. We investigate such radiation patterns for diffraction and for scattering from a horizontal reflector considering a background isotropic model. The radiation patterns show considerable potential for trade-off between the parameters and the potentially limited resolution in their recovery. The radiation patterns of C (sub 11) , C (sub 22) , and C (sub 33) are well separated so that we expect to recover these parameters with limited trade-offs. However, the resolution of their recovery represented by recovered range of model wavenumbers varies between these parameters. We can only invert for the short wavelength components (reflection) of C (sub 33) while we can mainly invert for the long wavelength components (transmission) of the elastic coefficients C (sub 11) and C (sub 22) if we have large enough offsets. The elastic coefficients C (sub 13) , C (sub 23) , and C (sub 12) suffer from strong trade-offs with C (sub 55) , C (sub 44) , and C (sub 66) , respectively. The trade-offs between C (sub 13) and C (sub 55) , as well as C (sub 23) and C (sub 44) , can be partially mitigated if we acquire P-SV and SV-SV waves. However, to reduce the trade-offs between C (sub 12) and C (sub 66) , we require credible SH-SH waves. The analytical radiation patterns of the elastic constants are supported by numerical gradients of these parameters.