Anomalous events, i.e., events other than simple reflections, are becoming more and more evident with the advent of magnetic tape and the various types of display sections such as variable area, variable density, full trace, etc. Recognition of these events, such as multiple reflections, diffractions, etc., is of considerable importance if the interpreter is to make optimum use of his data. A knowledge of the characteristics of the anomalous events likely to be encountered aids in their identification. Simple parameters, viz., arrival time, apparent dip stepout and normal moveout, readily obtained from the reflection seismogram, may be used to enable the problem to be approached quantitatively. Under the general headings: direct, refracted, reflected, and diffracted energy, air waves, surface waves, ghost reflections, simple multiples, complex multiples, diffractions, reflected refractions and refracted reflections are discussed. An example of a simple analytical attempt to solve an unusual offshore multiple problem is briefly described.

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