Seismic data compression by an adaptive local cosine/sine transform and its effects on migration

The local cosine/sine basis is a localized version of the cosine/sine basis with a window function which can have arbitrary smoothness. It has orthogonality and good time and frequency localization properties. The adaptive local cosine/sine basis is a best-basis obtained from an overabundant library of cosine/sine packets based on a costfunctional. We propose a 2D semi-adaptive (time-adaptive or space-adaptive) local cosine transform (referred to as a 2D semi-ALCT) and apply it to the SEG±EAEG salt model synthetic data set for compression. From the numerical results, we see that most of the important features of the data set can be well preserved even in the high compression ratio (CRˆ40:1) case. Using reconstructed data from the highly compressed ALCT coefficients (CRˆ40:1) for migration, we can still obtain a highquality image including subsalt structures. Furthermore, we find that the window partition, generated by the 2D semi-ALCT, is well adapted to the characteristics of the seismic data set, and the compression capability of the 2D semi-ALCT is greater than that of the 2D uniform local cosine transform (2D ULCT). We find also that a (32, 32) or (32, 64) minimum (time, space) window size can generate the best compression results for the SEG±EAEG salt data set.