GNGTS 2016 - Atti del 35° Convegno Nazionale

54 GNGTS 2016 S essione A matrice event above ML5.5 in the next day, computed at 00:00 of August 24, is equal to 10 -5 in the whole area, mainly given by the background rate. The inefficiency of the ETAS model to predict imminent sequences, following the occurrence of strong events, mainly derives from the poor modeling of the background. Firstly, the poissonian model neglects possible long-term temporal variations of the seismic rate (Marzocchi et al. , 2012). Second, the temporal window covered by instrumental catalogs should be too small to infer the actual spatial distribution of background. Regarding the second point, I compare the information coming from three different catalogs: the official INGV Bulletin, the instrumental CSIv1.1 (Castello et al., 2007; http://csi.rm.ingv.it/ ) and the historical CPTI15 catalogs (Rovida et al. , 2016; http://emidius.mi.ingv.it/CPTI15-DBMI15/) . Both the INGV Bulletin and the CSIv1.1 catalogues identify the areas around Norcia and Campotosto cities as the most hazardous regions (Fig. 3). Anyway, the size and the bounds of these areas are defined by the sequences included in the data (the 1997-1998 Colfiorito sequence, at north-west, for the CSIv1.1, and the 2009 L’Aquila sequence, at south-east, for the INGV Bulletin). The small size of the CPTI15 catalogue does not allow reaching detailed results. It seems to confirm what obtained from the other two catalogues, but assign a larger relative seismic potential to the area around Accumuli, struck by the 2016 earthquake (Fig. 3). These results show that the background spatial distribution should be inferred by integrating information coming from different type of catalogs. Hard work must be still done about the temporal distribution of background and the integration of further data. References Castello B., Olivieri M. and Selvaggi G.; 2007: Local and duration magnitude determination for the Italian earthquake catalogue (1981-2002) . Bull. Seism.Soc.Am., 97(1B), 128-139. Lombardi A.M.; 2015: Estimation of the parameters of ETAS models by Simulated Annealing . Sc. Rep., Feb 12;5:8417. doi: 10.1038/srep08417. Lombardi A.M.; 2016: SEDA a software package for the Statistical Earthquake Data Analysis: a tutorial application to the 2009 L’ Aquila and the 2012 Emilia (Italia) sequences. Ann. Geoph., submitted. Lombardi A.M.; 2016: SEDA a software package for the Statistical Earthquake Data Analysis . Sc. Rep., submitted. Fig. 3 – Comparison between the background spatial distributions obtained from three catalogs; the instrumental official INGV Bulletin, the CSIv1.1 and the historical CPTI15 catalogue. Gray circles mark the events below magnitude 2.5; orange circles, squares and stars mark the events with magnitude M<4.0, 4.0<–M<5.5 and 5.5<–M<6.5, respectively. Black stars marks the events with M>–6.5. The red stars mark the ML 6.0 and ML 5.4 events of the 2016 central Italy sequence, respectively, both occurred at August 24. The magnitude scales are ML for the INGV bulletin and CSIv1.1 and Mw for CPTI15.