MULTIFREQUENCY VISCOACOUSTIC MODELING AND INVERSION

Modeling and inversion for seismic wavefields that include the attenua tion and phase dispersion effects of Q can be implemented in the space -frequency domain. The viscoacoustic wave equation is solved by the mo ment method. Absorbing boundary conditions are implemented by reducing Q and adjusting the complex velocity (to reduce Q-dependent reflectiv ity) in a zone around the edges of the model grid. Nonlinear inversion is performed using iterative linearized inversions. The residual wave field at a single frequency is back projected, using an anticausal Gre en's function, along the viscoacoustic wavepath in an estimate of the model, to get updated velocity and Q distributions. The model obtained from data at one frequency becomes input to inversion at the next hig her frequency. Velocity and Q are inverted simultaneously as they are interdependent. Both modeling and inversion algorithms are successfull y tested with synthetic examples; data at two or three frequencies are sufficient to produce reliable images from noise-free synthetic data.