29-08-2017, 11:05 AM
The estimation of an accurate macro velocity model plays an important role in the seismic image and inversion of model parameters. Full waveform inversion (FWI) is the classic data domain investment method. However, the FWI mismatch function is highly nonlinear, and local optimization can not prevent the convergence of the mismatch function to local minima. To converge to the global minimum, FWI needs a good initial model or reliable low frequency component and long offset data. In this paper we present a reflection method based on the equation-based equation (WERTT), which can provide a good background model for FWI and pre-stack depth migration (LS-PSDM). First, the velocity model is decomposed into a lower-wave component (background velocity) and a high-wave component (reflectivity). Second, the primary reflection wave is predicted by the de-migration of the wave equation, and the reflection travel time is calculated by an automatic collection method. Finally, the misfit function of the l2 norm of the reflection path time residuals is minimized by a gradient-based method. Numerical tests show that the proposed method can invert a good background model, which can be used as an initial model for LS-PSDM or FWI.