GNGTS 2017 - 36° Convegno Nazionale

296 GNGTS 2017 S essione 2.1 Nekrasova A., Peresan A., Magrin A., Kossobokov V. (2016). The Unified Scaling Law for Earthquakes in the Friuli Venezia Giulia Region. Geophys. Res. Abstracts. Vol. 18, EGU2016-17706. Ogata, Y. (1998), Space-time point-process models for earthquake occurrences, Ann. Inst. Stat. Math. 50, no. 2, 379–402. Peresan A. and Gentili S. (2016). Caratterizzazione statistica di sequenze e sciami sismici nell’Italia Nord-Orientale. 35° GNGTS, Extended abstract, pp- 165-170. Rovida, A., Locati, M., Camassi, R., Lolli, B., Gasperini, P. Eds. (2016). CPTI15. Istituto Nazionale di Geofisica e Vulcanologia. doi :http://doi.org/10.6092/INGV.IT-CPTI15. Uhrhammer, R. (1986), Characteristics of Northern and Central California Seismicity, Earthquake Notes, 57 (1), 21. 9 Zaliapin, I., A. Gabrielov, H. Wong, and V. Keilis-Borok (2008). Clustering analysis of seismicity and aftershock identification, Phys. Rev. Lett., 101. Zaliapin, I. and Y. Ben-Zion (2013). Earthquake clusters in southern California I: Identification and stability. J. Geophys. Res., 118(6), 2847-2864, doi:10.1002/jgrb.50179. The power of the small ones L. Peruzza 1 with contributions of R. Gee 1,2 , M. Pagani 2 , G. Laurenzano 1 1 OGS, Centro di Ricerche Sismologiche, Trieste, Italy 2 GEM Foundation, Pavia, Italy Complex earthquake source models have being increasingly incorporated in probabilistic seismic hazard assessment (PSHA) by some countries. In Italy, we recently included in the modelling realistic geological complexities of non-rectangular faults, rough topography, and departure from traditional stationary assumptions, as is required during an ongoing seismic sequence or in volcanic contexts (Azzaro et al. , 2017; Peruzza et al. , 2016, 2017; Romano et al. , 2016). We briefly present an aftershock PSHA (sensu Yeo and Cornell, 2009) case study in Italy and the lessons learnt from it. In central Italy, after more than decennial investigations (e.g. Barchi et al. , 2000; Pace et al. , 2006; Peruzza et al. , 2011) and in the aftermath of the Amatrice 2016 sequence, we modelled aftershock seismic hazard due the complexVettore-Gorzano fault (Peruzza et al. , 2016). The high quality datasets of structural-geologic data enable us to model a complex fault source before that high quality hypocentral locations were available. By using a flexible seismic hazard software, e.g. the OpenQuake-engine (Pagani et al. , 2014) we proposed a seismic hazard estimate based on a time-dependent modelling of the decay of earthquake, after the deadly event of August, 24, 2016. In October the seismic sequence rejuvenates, with another M~6 earthquake near Visso, followed on October 30 by the “main” event right now, a M~6.5 in the Norcia area. We therefore updated our model, to include the queues of these new events, and we computed the ground motion expected to be exceed at a given probability level during several time frames, in a retrospective and prospective mode. Results clearly shows how minor earthquakes (i.e. M<5) contribute to the aftershock hazard curve, at epicentral/near field distances. The availability of temporary and permanent stations in the area enabled us to perform a validation test, by comparing APSHA and empirical hazard curve at some sites (Gee et al. , 2017). We demonstrate that the small magnitudes events have a strong impact on shaking forecasts, thus driving the rebuilding/retrofitting strategies for risk reduction. References Azzaro R., G. Barberi, S. D’Amico, B. Pace, L. Peruzza, T. Tuvè (2017) When probabilistic seismic hazard climbs volcanoes: the Mt Etna case, Italy. Part I: model components for sources parametrization. Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2017-127.