Abstract

It is known that seismic traces are often characterized by quasi-periodic oscillations which are nearly sinusoidal. A comparison between these field seismic traces and the corresponding synthetic seismograms, as computed from velocity logs, shows that these continuous oscillations are due partly to secondary arrivals which are mutually interfering and partly to seismic "noise". The main arrivals of reflected energy superimpose and interfere with these continuous oscillations; consequently, it is difficult to pick reflections accurately. This paper considers methods of eliminating these continuous oscillations from the seismic sections, and of bringing out the energy content of the seismic waves in order to outline the changes in reflection energy which are superimposed upon the common and almost constant background energy arising from secondary arrivals and from noise.From the commonly known expressions of kinetic energy and potential energy of compression in vibrating solids, it has been possible to design a suitable computer for obtaining film cross-sections which are the energy cross-sections, so-called because they show the energy arrivals. Another possibility is to calculate correlations between successive seismic traces (adjacent or not) and to do this only for dips which may possibly be reflected arrivals. It has also been possible for this case to design a suitable computer and to add to the playback unit a system for presenting correlations. This system uses a cathode-ray tube equipped with an optical projection system which gives the possibility of automatically applying small segments of a line or vector with an inclination equal to the apparent dip of the reflection and with a thickness proportional to the strength of the reflection; thence the name of "vector section" given to this section. After a short resume of the principles which are fundamental to these processes, the practical results obtained by the two methods are described and discussed, and a comparison between their relative advantages is given.

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