MIGRATION BY PHASE-SHIFT - ALGORITHMIC DESCRIPTION FOR ARRAY PROCESSORS

The phase shift method (Gazdag, 1978) is based on the solution, in the frequency domain, of an approximation (Glaerbout, 1976) to the one-way wave equation with initial conditions defined by a zero-offset seismic section. Wave velocity is assumed to be constant within each layer of the section grid and is allowed to vary from layer to layer. Under these conditions, the equation written in the frequency domain reduces to a system of independent ordinary differential equations with initial values that can be solved analytically for each layer. The integration process simply amounts to multiplying the initial values by a complex number of unit modulus. The main advantages of this method are simplicity, stability, and high accuracy, since the precision of the Fourier approximation is limited only by the granularity of the seismic section.-Authors