Migration velocity analysis using prestack wavefields

Using both the image and data domains to perform velocity inversion can help us resolve the long and short wavelength components of the velocity model, usually in that order. This translates to integrating migration velocity analysis (MVA) into full waveform inversion (FWI). The MVA part of the inversion often requires computing extended images, which is pricy using conventional methods. As a result, we use prestack wavefield (the double-square-root (DSR)) extrapolation, which includes the extended information (subsurface offsets) naturally, to make the process far more efficient and stable. The combination of the forward and adjoint prestack wavefields provides us with update options that can be easily conditioned to improve convergence. We, specifically, use a modified differential semblance operator to divide the extended image to the residual part for classic differential semblance operator (DSO) updates and the image modeling part, which provides reflections for higher resolution information. In our implementation, we invert for the velocity and the image simultaneously through a dual objective function. Application to the Marmousi model demonstrates the features of the approach.