Gradients for wave‐equation migration velocity analysis

Abstract

Wave‐equation migration velocity analysis (WEMVA) is an image‐domain tomography based on a wave‐equation propagator (one‐way or two‐way). Different algorithms for residual calculation, propagation and optimization add varying flavors to WEMVA. The two most popular ways to compute the residual are either using differential semblance optimization (DSO) or using differential residual migration (DRM). In this paper, we present relevant theory to understand the difference these two algorithms make in the final gradient calculation. We compare and contrast the two methods with the help of numerical examples. Both methods have some advantages and disadvantages over the other and they should be kept in mind while making the choice. The theory and results presented are based on one‐way wave‐equation migration.