Statistical tools in the analysis of macroseismic fields for probability modelling of the attenuation analysis of macroseismic

Information content of a macroseismic field is generally summarized by tracing the isoseismals. A simple examination of a series of fields on the basis of these curves fully proves the complexity of the problem to identify a global pattern among the trends of decay of the macroseismic intensity shown by the various earthquakes. This investigation raises some questions on: 1) the dependence of the decay pattern on the epicentral intensity; 2) the existence of a specific shape for the isoseismals in a seismogenic zone; 3) the way in which the velocity of the decay changes as a function of the epicentre-site distance; 4) the possible correlation among shape of the isoseismals and some tectonic features; 5) how to quantify and include into the model the various sources of uncertainty inherent in the phenomenon.