Effects of the Near Field on Source-independent Q Estimation

We consider the problem of Q estimation from microseismic and from perforation shot data. Assuming that the source wavelet is not well known, we focused on the spectral ratio method and on source-independent viscoelastic full waveform inversion. We derived 3-D near-field approximations of monopole and dipole Green's tensors in a homogeneous viscoelastic medium. We show that the spectral ratio method is not applicable in the near-field region, but a two-step source-independent viscoelastic full waveform inversion strategy applied to synthetic data can first recover the purely elastic velocities and then provide an attenuation estimate.