Abstract Seismic coherence is used to detect discontinuities in underground media. However, strata with steeply dipping structures often produce false low coherence estimates and thus incorrect discontinuity characterization results. It is important to eliminate or reduce the effect of dipping on coherence estimates. To solve this problem, time-domain dip scanning is typically used to improve estimation of coherence in areas with steeply dipping structures. However, the accuracy of the time-domain estimation of dip is limited by the sampling interval. In contrast, the spectrum amplitude is not affected by the time delays in adjacent seismic traces caused by dipping structures. We propose a coherency algorithm that uses the spectral amplitudes of seismic traces within a predefined analysis window to construct the covariance matrix. The coherency estimates with the proposed algorithm is defined as the ratio between the dominant eigenvalue and the sum of all eigenvalues of the constructed covariance matrix. Thus, we eliminate the effect of dipping structures on coherency estimates. In addition, because different frequency bands of spectral amplitudes are used to estimate coherency, the proposed algorithm has multiscale features. Low frequencies are effective for characterizing large-scale faults, whereas high frequencies are better in characterizing small-scale faults. Application to synthetic and real seismic data show that the proposed algorithm can eliminate the effect of dip and produce better coherence estimates than conventional coherency algorithms in areas with steeply dipping structures.
This work was sponsored by National Key S & T Project of China (No. 2011ZX05004-003), and the Research Program of RIPED (No. 101002kt0b52135).
Cite this article:
Sui Jing-Kun,Zhang Xiao-Dong,Li Yan-Dong. A seismic coherency method using spectral amplitudes[J]. APPLIED GEOPHYSICS, 2015, 12(3): 353-361.
[1]
Bahorich, M., and Farmer, S., 1995, 3D seismic discontinuity for faults and stratigraphic features: The Leading Edge, 14(10), 1053−1058.
[2]
Claerbout, J. F., 2008, Basic earth imaging, Citeseer, 66−69.
[3]
Dou, X. Y., Han, L. G., Wang, E. L., et al. 2014, A fracture enhancement method based on the histogram equalization of eigenstructure-based coherence. Applied Geophysics, 11(2), 179−185.
[4]
Gabor, D., 1946, Theory of Communication: IEEE, 93, 429−457.
[5]
Gersztenkorn, A., and Marfurt, K. J., 1999, Eigenstructure based coherence computations as an aid to 3D structural and stratigraphic mapping: Geophysics, 64(5), 1468−1479.
[6]
Kazmi, H. S., Alam, A., and Ahmad, S., 2012, High resolution semblance using continuous amplitude and phase spectra: 82th Ann. Internat. Mtg, Soc. Expl. Geophys., Expanded Abstracts, 31, 1−5.
[7]
Li, F., and Lu, W., 2014, Coherence attribute at different spectral scales: Interpretation, 2(1), 1−8.
[8]
Li Y., Lu, W., Xiao, H., Zhang S., and Li, Y., 2006, Dip-scanning coherence algorithm using eigenstructure analysis and supertrace technique: Geophysics, 71(3), 61−66.
[9]
Marfurt, K. J., 2006, Robust estimate of 3D reflector dip and azimuth: Geophysics, 71(4), 29−40.
[10]
Marfurt, K. J., Kirlin, R. L., Farmer, L. S., and Bahorich, M. S., 1998, 3D seismic attributes using a semblance based coherency algorithm: Geophysics, 63(4), 1150−1165.
[11]
Wang, J., and Lu, W. K., Coherence cube enhancement based on local histogram specification: Applied Geophysics, 2010, 7(3), 249−256.
[12]
Wang, X., Yang, K., Liu, Q., Yang, W., Liu, H., and Li, Y., 2002, Research on algorithm of seismic coherent cube based on wavelet transform: Oil Geophysics Prospecting, 37(4), 328−331.
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