The intensity attenuation of Colfiorito and other strong earthquakes: the viewpoint of forecasters and data gatherers

R. Rotondi, A. Tertulliani, C. Brambilla, G. Zonno


This article has been originated by thoughts on previous analyses related to the proba-
bilistic treatment of the macroseismic attenuation, from which it turns out that in Italian
territory the intensity decay I varies greatly from one region to another, depending on
many factors, some of them not easily measurable. By applying a clustering algorithm
we classified some macroseismic fields drawn from the Italian felt report database in three
classes. Earthquakes into the same class constituted the input of a two-step procedure for the
Bayesian estimation of the probability distribution of I at any distance from the epicenter,
conditioned on I0, where I is considered an integer, random variable, following a binomial
distribution. The estimated distributions were validated by forecasting the macroseismic
field of the Colfiorito earthquake. In this article we deal with the issues left open by those
statistical analyses by following two ways: on one hand we test the procedure by forecasting
the macroseismic field of other strong earthquakes recorded in Italy during the last century
and, on the other hand, we ask the reasons of peculiarities in the results to experts in other
fields. The article is hence an introductory work, an example of the possibility and of the
need of exchange of knowledge.


Attenuation – Forecast – Macroseismic intensity – Seismic scenario – Validation criteria.

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X