THE SECTIONAL AUTO‐CORRELOGRAM AND THE SECTIONAL RETRO‐CORRELOGRAM *

ABSTRACT The auto‐correlation function of a seismic trace contains information on all the multiple reflection activity present in the trace. The interpretation of this information is facilitated by the arrangement of autocorrelation functions in cross‐sectional form, in the manner of a normal record section. This is the concept of the Sectional Auto‐Correlogram. Specifically, the Sectional Auto‐Correlogram will. Show if the record section does not include significant multiples, thus allowing confident picking of the primary reflections. Show if the record section does include significant multiples, giving their travel times and inclinations (and, under certain circumstances, their reflection coefficients). Indicate by what process the multiples should be treated. Yield an authoritative measure of the success of a multiple‐attenuating treatment. Delineate shallow horizons, even those whose primary reflections are too early to be recorded satisfactorily. Give the true travel time of a primary reflector, and the sign of its reflection coefficient. The Sectional Auto‐Correlogram allows the study of primary reflectors by consideration of the multiples generated by them, and in this sense may be said to turn multiple reflections to advantage. Thus a primary reflection at a certain time is defined if we find that every reflection on the record is followed by a multiple after this certain time. Alternatively, a primary reflection at a certain time is defined if, after that certain time, we can find a repetition of the entire record. The Sectional Auto‐Correlogram also has secondary uses in fault identification, crustal studies and weathering problems.