Effect Of Normal Moveout On A Seismic Pulse

Using a synthetic seismogram as input, normal moveout correction stretches a reflection pulse in such a way that the spectrum of the pulse is a linearly compressed version of the uncorrected pulse spectrum. The amount of compression depends on t0, the source-detector separation, velocity, and the rate at which velocity varies with t0. The amplitude of the spectrum is increased by the same factor that expresses the spectral compression. As a result, the summed pulse from a CDP stack is richer in low frequencies than one might anticipate and has a smaller signal-to-noise ratio than the square root of the number of traces in the stack.