MACROSEISMIC ESTIMATES OF MAGNITUDE IN ITALY

A multi-parametric study of empirical relationships between macroseismic data and magnitude is presented for the Italian region by the analysis of a new extended data set concerning 146 earthquakes. The available magnitude determinations include all of the most intense earthquakes which occurred in Italy in the last century and have been obtained by an accurate revision of original instrumental data. Intensity data have been revised and upgraded on the basis of the most recent studies: only local intensities directly documented have been used. Macroseismic determinations of M(s), m(B) and M(wa) magnitudes have been performed. The empirical relationships between maximum felt intensity (I-max) and magnitude have been determined by the use of a distribution-free approach and a linear regression analysis. This last parameterization allows for the explanation of more than 60% of the Variation in magnitude. In order to improve these results, the linear dependence between magnitude, I-max and average distances (in logarithm) corresponding to fixed attenuation values has been explored. The comparison between instrumental magnitudes and corresponding macroseismic estimates obtained From empirical relationships shows that the respective uncertainties are comparable.