In situ dynamic characterization of natural granular soils by means of V S values is accomplished by direct and indirect investigation techniques. Integration among those types of field test are encouraged by Eurocode 8 through correlations amongst V S and N SPT but this does not suggest the best correlation formulation among the ones presented over the last thirty years. Besides such correlations can provide highly disperse values of V S . Thus a rational design of investigation campaign and

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... asurement interpretation and calculations appears to play an important role in dynamic characterization of granular soils accomplished by in situ tests. It should rely on selecting the best fitting correlation formulations site by site according to soil types, their random structures and the characteristics of investigation techniques measured dynamic soil properties. An application of statistical approach to the issues previously sketched is carried out in the Pomigliano d'Arco urban area where Down-Hole and Standard Penetration tests were performed for dynamically characterizing the foundation soils. Assessment of uncertainties in V S values should allow the performance of hazard analyses and reliability-based design in seismic areas.