Prestack depth migration in elliptic coordinates

Jeff Shragge and Guojian Shan

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ABSTRACT

We extend Riemannian wavefield extrapolation (RWE) to prestack migration using 2D elliptic coordinate systems. The corresponding 2D elliptic extrapolation wavenumber introduces only a slowness model stretch to the single-square-root operator, enabling the use of existing Cartesian implicit finite-difference extrapolators for propagating wavefields. A zero-offset migration example illustrates the advantages of elliptic coordinates in imaging overturning wavefields. Imaging tests of the SMAART JV Pluto 1.5 and BP velocity benchmark data sets illustrate that the RWE migration algorithm generates high-quality prestack migration images equal to, or better than, the corresponding Cartesian coordinate systems. We still require higher-order extrapolators for accurate propagation and imaging using one-way wave equations, even in situations where RWE geometries are employed.