Page 384 - Acquisition and Processing of Marine Seismic Data

7.2 PREDICTIVE DECONVOLUTION 375

FIG. 7.10 (A) Amplitude attenuation rates of multiples for a range of prediction lag and operator length values.
(B) A synthetic trace with one primary reflection (P) and its multiple (M) used for the analysis in (A). (C) The autocorrelogram
of the synthetic trace in (B), indicating that the multiple period and time length of the wavelet are 100 and 28 ms, respectively.

in Fig. 7.10C, the multiple period and time length first-order multiple in the autocorrelation series.
of the wavelet are 100 and 28 ms, respectively. When the prediction lag exceeds the multiple
Based on the analysis in Fig. 7.10A, the maxi- period, multiple attenuation simply fails regard-
mum attenuation in multiple amplitude is lessoftheoperatorlength(Fig.7.10A).Asaresult,
obtained when the prediction lag equals the mul- operator length must be selected as close as pos-
tiple period (100 ms) regardless of the operator sible to the length of the source wavelet embed-
length. Although the attenuation is not widely ded in the data, and the prediction lag must
affected by operator length, the decay in the mul- equal to the multiple period which it is intended
tiple amplitude slightly decreases for higher tosuppress.Thetimelengthofthesourcewavelet
operator lengths if the prediction lag is small is the length ofthe firstisolatedenergypackagein
(e.g., compare the decay curve of 36-ms operator the autocorrelogram (Fig. 7.10C). If smaller, it
length for a prediction lag range between 60 and progressively corresponds to a deconvolution
95 ms). In any case, the multiple suppression is application for the temporal resolution improve-
maximum when the prediction lag exactly equals ment (Section 6.5). In any case, the prediction
the multiple period. The multiple period is the lag must not exceed the multiple period for a
time span between the multiples in the seismo- successful multiple elimination.
gram and can be obtained by analyzing the auto- Fig. 7.11 shows an analysis of multiple sup-
correlogram of the input trace. Practically, the pression by predictive deconvolution on a syn-
multiple period equals the onset time of the thetic minimum phase trace consisting of a