SEISMIC HAZARD ANALYSIS - HOW TO MEASURE UNCERTAINTY

Applications of probabilistic seismic hazard analysis demand the adopt ion of a model (i.e. of the forms of a certain number of correlations and probabilistic distributions) and the estimate of the parameters of the model. As a measure of uncertainty in the calculation of the expe cted value of a given quantity (for instance the peak ground accelerat ion corresponding to a given return period at a given site) a coeffici ent of variation is frequently adopted, which is intended to include u ncertainties due to both the choice of the model and the estimate of p arameters. The following three statements are illustrated in this pape r: (1) in theory, the use of a coefficient of variation, when uncertai nties in modeling are involved, is not correct, (2) in practice, the a foresaid use can lead to unreliable results and (3) the analysis of un certainties can be carried out in a more satisfactory way if uncertain ties in modeling and uncertainties in the estimate of parameters are c onsidered separately and viith different approaches. (C) 1998 Elsevier Science Ltd. All rights reserved.