An analysis leading to the reduction of scattered noise on deep marine seismic records

Abstract

The rough and uneven basaltic basement in deep marine environments functions as a potential source of scattering. The source‐generated noise not only interferes with the weak and deep primary reflections, but often resembles primary reflections, thereby confusing the seismic interpretation. An analysis of the arrival time of scattered noise indicates that NMO and apparent dip of scattered noise exhibit azimuth dependence. For isotropic scattering, in‐line scattering at ranges near 0 degree azimuth and sideswipe from 90 degree azimuth should dominate the seismic section. Actual marine data displayed in various data gathers illustrate these characteristics of scattered noise and also correct a common misconception about the appearance of scattered noise. The analysis suggests the use of CDP stacking and velocity filtering to attenuate the scattered noise. The combined effect shows a total reduction of scattered noise by 21 dB for the frequency bandwidth from 20 to 32 Hz.