Frequency Decomposition of Broadband Seismic Data: Challenges and Solutions

by: P. Szafian* (ffA), J. Lowell (ffA), A. Eckersley (ffA) & T. Kristensen (Lundin Norway)

Frequency decomposition is a widely used method for identifying and discriminating different geological expressions in the seismic data by isolating seismic signals of particular frequency ranges. Several frequency decomposition techniques are available for the interpreter: each utilises different filtering methods, resulting in a variety in their resolution in time and frequency (e.g. Castagna and Sun 2006; McArdle and Ackers 2012). 

The highest vertical resolution is achieved by a method based on a matching pursuit approach (Mallat and Zhang, 1996), whereby Gabor wavelets at different frequencies and phase rotations are matched to a seismic trace in an iterative process according to the highest spectral energy. Using the matched wavelet set, a band-limited trace can be reconstructed within a given frequency interval. This method offers a particularly high resolution vertical localisation in comparison to other methods; however, it is partial to the dominant frequency of the seismic data and occasionally fails to consistently match wavelets to the relatively low energies at the low and high frequencies. 

An example broadband trace (left), its spectrogram (middle) with the limiting frequencies indicated in white and the band-limited reconstructions (right) for the three frequency bands.

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