STABILITY OF PREMONITORY SEISMICITY PATTERN AND INTERMEDIATE-TERM EARTHQUAKE PREDICTION IN CENTRAL ITALY

The algorithm CN makes use of normalized functions. Therefore the orig inal algorithm, developed for the California-Nevada region, can be dir ectly applied, without adjustment of the parameters, to the determinat ion of the Time of Increased Probability (TIP) of strong earthquakes f or Central Italy. The prediction is applied to the events with magnitu de M greater than or equal to M(0) = 5.6, which in Central Italy have a return period of about six years. The routinely available digital ea rthquake bulletins of the Istituto Nazionale di Geofisica (ING), Rome, permits continuous monitoring. Here we extend to November 1994 the fi rst study made by Keilis-Borok et al. (1990b). On the basis of the com bined analysis of seismicity and seismotectonic, we formulate a new re gionalization, which reduces the total alarm time and the failures to predict, and narrows the spatial uncertainty of the prediction with re spect to the results of KEILIS-BOROK et al. (1990b). The premonitory p attern is stable when the key parameters of the CN algorithm and the d uration of the learning period are changed, and when different earthqu ake catalogues are used. The anlysis of the period 1904-1940, for whic h M(0) = 6, allows us to identify self-similar properties between the two periods, in spite of the considerably higher seismicity level of t he earlier time interval compared with the recent one.