Suppression Method Of Ground Roll In Seismic Data Processing

Ground roll,as a strong interference wave in seismic exploration,reduces the signal-to-noise ratio and the resolution of seismic data.Existing suppression methods of ground roll mostly based on the frequency characteristics or velocity characteristics of ground roll.Unfortunately,they damage the low frequency component of effective waves in the suppression of ground roll.Therefore,how to suppress ground roll without damaging effective wave,achieve high signal-to-noise ratio,high resolution,high fidelity in processing is the main research content in this paper.Based on the wave generation mechanism and propagation basic theory of ground roll,we calculate dispersion curves using the ground roll propagation equations,then acquire synthetic records of ground roll and analyze the corresponding relationship between the dispersion curve and ground roll profile,as well as the influence of the longitudinal wave velocity,shear wave velocity,density and thickness parameters on the shape of dispersion curve.Through the analyses,we clear the theory and effect of existing suppressing methods in ground roll suppression processing,such as frequency-wave number filter,regional filtering,zone abnormality process,etc.Ground roll seems to be "visual" linear interference rather than mathematical linear interference because of its dispersion characteristics in actual data.Ground roll and effective waves overlap each other on frequency-wave number spectrum,which makes frequency-wave number filter unable to obtain ideal ground roll suppressing effect.Therefore,"inverse" dispersion method is put forward in this paper: using phase correction eliminates travel time differences caused by ground roll dispersion on common shot gathers,restores the "broom-like" ground roll to linear interference in profile,and then using frequency-wave number filter removes ground roll.Proved by model trial,the "inverse dispersion" method gives the desired results in processing.