In the second stage, one provides a propagation model relevant to historical epicentre sites; this phase is based on the development of a statistical procedure finalized to determine the seismic epicentres distribution in a region where macro- seismic characters of previously occurred earthquakes are known.

In details the paper is devoted to the study of seismic zoning; this objective is pursued by developing a statistic method based only on the knowledge of the main macro-seismic parameters, such as the seismic magnitude, intensity and epicentre co-ordinates, characterizing previously occurred earthquakes at each site; these data are needed in order to search for the probability function localizing the seismic epicentres . Once fixed the earthquake magnitude, the shape of the localization probability function is assumed to be gaussian and given by the suitable coupling of a number of gaussian functions.

Then the final expression of the localization function is obtained by combining the single contribution of the involved gaussian functions by means of some relevant convex combination coefficients . In order to completely determine the probability function the unknown parameters related to the single gaussian function should be determined, i.e. the average values of the epicentre co-ordinates and , the variances and the correlation coefficient ; moreover for operating the final assemblage the convex combination coefficients should be also determined. In order to do this it is necessary to solve a number of expressions of statistical moments related to the maximum order of trough a suitable equation (therefore ).

Hence, the parameters are evaluated by operating a fitting process; the final set of "fitting" values is searched for by minimizing the mean square error of the current moments for the given set of parameters, and of the average moments calculated on the basis of historical data as functions of parameters and constrained by suitable conditions.

In the final part of the paper, one reports a numerical application, where the above mentioned procedure is developed for earthquakes occurred in a predefined time range with varying intensities, whose epicentre is located in a given seismic area. Numerical results show a good agreement with previously obtained results, demonstrating that the proposed approach ensures a good approximation of the combined probability curves.

1

Baratta, A., "Dynamics of a Single-Degree-of-Freedom System with a Unilateral Obstacle", in Structural Safety, N.8, pp. 181-194, 1990. doi:10.1016/0167-4730(90)90039-R

2

Baratta, A., Cacace, F., "Modello probabilistico di pericolositá finalizzato all'analisi di rischio sismico" in "Omaggio a Giulio Caradini", Dept. of Structural and Geotecnical Engineering, ESAGRAFICA, Rome, 1988.

3

Baratta, A., Cacace, F., "Modello probabilistico per l'analisi della distribuzione epicentrale", Proc. of the 5th National Congress "L'Ingegneria Sismica in Italia", Palermo, 1991.

4

Baratta A., Zuccaro G., "Un Modello Reticolare per lo Studio della Distribuzione dell'Intensitá Sismica sul Territorio" Proc. of the 4th National Congress "L'Ingegneria Sismica in Italia", Milano, 1989.

5

Boschi, E., Ferrari, G., Gasperini, P., Guidoboni, E., Smriglio, G., Valensise, G., "Catalogo dei forti terremoti in Italia dal 461 a.C. al 1980, ING-SGA, 970 pp., Bologna, 1995.

6

INGV, "Bollettino Macrosismico", 1981-1997.

7

Romeo, R., Pugliese, A., "A global earthquake hazard assessment of Italy", ECEE '98, Paris, 1998.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £125 +P&P)