Reduction of crosstalk in blended-shot migration

Jörg Schleicher, Jessé C. Costa, Amélia Novais
2015 Geophysics  
When migrating more than one shot at the same time, the nonlinearity of the imaging condition causes the final image to contain the so-called crosstalk, i.e., the results of the interference of wavefields associated with different sources. In this work, we study various ideas of using weights in the image condition, called encoding, for the reduction of crosstalk. We combine the ideas of random phase and/or amplitude encoding and random alteration of the sign with additional multiplication with
more » ... multiplication with powers of the imaginary unit. This procedure moves part of the crosstalk to the imaginary part of the resulting image, leaving the desired crosscorrelation in the real part. In this way, the final image is less impaired. Our results indicate that with a combination of these weights, the crosstalk can be reduced by a factor of 4. Moreover, we evaluate the selection procedure of sources contributing to each group of shots. We compare random choice with a deterministic procedure, where the random numbers are exchanged for numbers similar to those of a Costas array. These numbers preserve certain properties of a random choice, but avoid the occurrence of patterns in the distribution. The objective is to avoid that nearby sources can be added to the same group of shots, which cannot be guaranteed with a random choice. Finally, we show that the crosstalk noise can be reduced after migration by image processing.
doi:10.1190/geo2014-0293.1 fatcat:7xcwgjiqefdsvpder6gre3x3qu