A Note on Signal Distortion Due to Dynamic (Nmo) Corrections*

By applying dynamic corrections a seismic trace recorded at a distance x from the energy source should be varied in such a way as to obtain a trace which would be recorded at zero‐distance, i.e. at the source itself. Only such a zero‐offset‐trace contains the correct sequence of reflection coefficients (reflectivity function), whilst all other traces contain a distorted reflectivity function. In the simplest case, the reflectivity function is compressed over a shorter time whereas in more complicated cases a partial inversion of the reflectivity function results. This happens when some of the reflection hyperbolae intersect one another. The reconstruction of the true zero‐offset reflectivity function by the application of dynamic corrections can only be an approximative process. In the first case mentioned we must expect a decrease in accuracy of the corrected trace in comparison with a zero‐offset‐trace. In the second case, where intersections of the hyperbolae occur, accurate reconstruction is clearly impossible. The problems are discussed with the help of theoretical and practical examples.