ELIMINATION OF SEISMIC GHOST REFLECTIONS BY MEANS OF A LINEAR FILTER*

A technique is described for elimination of ghost reflections on magnetically recorded seismograph records by means of a linear filter. The application of this filter does not alter the character of primary reflections although eliminating the ghost reflections. The principal assumption made in the develop-ment of the technique is that the effect of AGC in altering the amplitude ratio of primary and ghost reflections is uniform for all record time A realization of the required filter is given and a measurement technique is outlined for detecting the existence of ghost reflections based on the autocorrelation function of the seismograph trace. The existence of a large velocity discontinuity above a seismic shot has long been recognized as the source of “ghost ” reflections appearing on the seismogram In such instances, the downgoing wavefront set up by the shot is characterized by energy moving directly downward from the shotpoint followed in space and time by energy reflected from the overlying discontinuity. When detected, this downgoing wavefront appears as two wavelets displaced in time by approxi-mately twice the travel time from the shot to the discontinuity and with possibl