Globally optimized fourier finite-difference operator using simulated annealing algorithm based on multi-parameter

Fourier finite-difference (FFD) method can handle wave propagations in the complex media with large lateral velocity contrasts and wide propagation angles. However, the FFD method has obvious error for wider angles. The optimization method can obviously improve the image accuracy of wider angles without additional computational cost. Based on the rational approximation of the FFD operator, we extend the two coefficients to be optimized to four coefficients, then we optimize them globally using simulated annealing algorithm. Besides the velocity contrast, we consider the effects of both frequency and depth interval. The theoretical analyses and the impulse responses demonstrate that our method significantly extends the accurate propagation angle of the FFD method. Migration results on the 2D SEG/EAGE salt model show that our method resolves the wider angles and the sub-salt weak reflectors more accurately than the unoptimized FFD method. Combination of the FFD method and alternative-direction- implicit plus interpolation method on 3D impulse responses further proved the validity of our method.