Evaluation of Anelastic Effects in Seismic Waveform Inversions

The results of a synthetic study on anelastic effects in seismic full waveform inversions are presented. It is shown that the application of a pure acoustic waveform inversion algorithm does not yield satisfactory results when the data to be inverted are acquired in a viscoacoustic medium. A frequency-domain viscoacoustic waveform inversion algorithm is developed through the use of complex velocities. The sensitivity functions for perturbations in both the real and imaginary velocities are derived explicitly. The new algorithm provides the capability to reconstruct both the velocity and the Q distribution of the subsurface, which is an intrinsic rock property that is of interest in many applications. Results of viscoacoustic inversions show that a better fit between the modeled and observed data is obtained than with pure acoustic inversions. The relative Q distributions carry information on the attenuation properties of the subsurface. Furthermore, it is shown that when the source functions are unknown, and hence must be inverted for as well, part of the attenuation effects can get incorporated into the source functions.