Page 271 - Acquisition and Processing of Marine Seismic Data

262 5. PREPROCESSING

FIG. 5.20 Effect of time domain length of the filter operator on the shape of the pass-band region in the frequency domain
for the filter operators of (A) 100 ms, (B) 200 ms, (C) 400 ms, and (D) 600 ms lengths (left panels) and their corresponding
amplitude spectra (right panels). The operator is designed as a 40–210 Hz band-pass filter with 10-Hz transition bands.

reflections and filtering out this frequency band systematic appearance) and reflection signal
can degrade the low-frequency deeper reflection amplitudes at the same time. In marine seismic
amplitudes. Although some recent studies exist applications, the most effective factors deter-
in the literature to remove swell noise without mining the data frequency band are the source
degrading the low-frequency signal amplitudes frequency and the source and/or streamer
(e.g., Dondurur and Karslı, 2012), band-pass fil- depths (Section 2.5.1.2). When we omit the
tering is widely used today to remove the swell effects of source and streamer depths and hence
noise from raw marine shots. the effect of ghost reflection interference, nor-
It is practically not possible to designate an mally the larger the source signal spectrum,
estimation of the frequency components of the the wider the recorded data frequency band.
recorded signal because the data spectrum is The Nyquist frequency determined by the sam-
formed by both noise (which sometimes has a pling rate controls the maximum frequency