Application of refraction tomography algorithms to real data

Abstract

We applied two wave-based refraction traveltime tomography algorithms to a real, field data set obtained in Congo, Gulf of Mexico. The two wave-based refraction tomography methods extract traveltimes by taking the logarithm of damped wavefield. The damped wavefield can be assumed to have a single, first arrival when we choose an optimal damping factor in complex angular frequency. The main differences between two methods exist in computing the steepest-descent directions. One method computes Frechet derivative of traveltime directly; The other method introduces a backpropagation algorithm and virtual source concept, which is commonly employed in waveform inversion and reverse time migration. The two methods have already proven to give similar, good results for synthetic data. After applying the two wave-based tomography methods to the real, field data, we can know that both of them describe high-velocity salt dome structure very clearly and give reliable solutions for real data. Having used the inverted velocity model in prestack Kirchhoff migration successfully, we can also confirm that the inverted velocity model obtained by the refraction tomography method can be effectively applied in prestack Kirchhoff migration.