f CREDIBILITY OF THE OPTIMUM XY SPACING OF THE GENERALIZED RECIPROCAL METHOD IN INTERPRETATION OF SHALLOW REFRACTION SEISMIC DATA

The shallow seismic refraction technique has inherent problems, such as the undetected layers, ambiguities, first and later arrivals. Other main problems are related to the interpretation techniques themselves. Most of them are restricted to simple models, but the generalization is responsible to false interpretations The Generalized Reciprocal Method (GRM) is suggested to be used for mapping subsurface structures with lateral variations. This method depends mainly on a heuristic single parameter called the optimum XY distance. At the optimum XY separation, the rays to each geophone emerge from near the same point on the refractor. Since the GRM has heuristic assumptions and has no mathematical derivation, more uncertainties are raised in its application, even in case of simple models. The lack of constant XY spacing in all cases (except the horizontal ones) will lead to more uncertainties in its application. The optimum XY value is based on a heuristic determination and it is always a doubtful matter. The uncertainties of the optimum XY spacing will be discussed on two synthetic models.