GNGTS 2013 - Atti del 32° Convegno Nazionale

motion. In this way, for each site, a number of ground motion synthetics become available. The synthetics can be statistically analyzed to evaluate the probability distribution of ground motion values (PGA, PGV, PSA, etc.). In this studywe present a prototype of the database SYNTHEtic SeISmograms (SYNTHESIS 0.1). It is designed to archive and distribute synthetic waveforms computed for earthquake hazard analysis and engineering applications. The database is complemented with all associated information describing each scenario-event. The structure of SYNTHESIS is adopted from the ITACA database (http://itaca.mi.ingv.it) , developed to archive and distribute recorded strong motion data in Italy. The main features of the SYNTHESIS database and the web portal for data dissemination are illustrated. The web database can be accessed at http://dyna.mi.ingv . it/synthesis/. A wide range of search tools enables the user to interactively retrieve synthetic waveforms, parameters of the scenario-events and geographic information on simulation sites. A range of display options allows users to view data in different contexts, extract and download synthetic waveforms and display maps of selected peak ground parameters. Simulation techniques. Seismic scenarios reported in the SYNTHESIS database are characterized by various complexity levels which are defined by the typology of the computing techniques used to simulate seismograms. In the first release of the database we have considered seismograms generated by stochastic (EXIM: Motazedian and Atkinson, 2005), deterministic- stochastic (DSM: Pacor et al. , 2005) or hybrid methods (HIC: Gallovič and Brokešová, 2007), as summarized in Tab. 1. Deterministic methods are those that can reproduce in a more realistic way the path effects in a well defined heterogeneous media through a full numerical simulation of the fault-to-site wavefield. On the other hand, they require a greater amount of computational resources. Stochastic finite fault methods, in spite of their theoretical limitations, are more efficient in terms of computational resources, and can be widely used to simulate accelerograms in the engineering frequency-range of interest (0.2 - 20 Hz). Scenario-event. In the SYNTHESIS prototype database we have included the case of the 1980 Irpinia earthquake (M 6.9). This earthquake was the largest seismic event ever recorded in Southern Italy by strong motion instruments (Cocco and Pacor, 1993; Improta et al. , 2003; Cultrera et al. , 2010; Ameri et al. , 2011). It was recorded by only 21 analog accelerometric stations, 8 of them located close to the source (R jb < 40 km), belonging to the National Accelerometric Network (RAN, Rete Accelerometrica Nazionale) operated by Italian Department of Civil Protection (DPC). This event was characterized by subsequent rupture episodes of three distinct normal fault segments. For simplicity, we considered just the first strongest rupture episode that occurred on a NW-SE oriented and NE dipping fault plane (Length = 35 km, Width = 15 km, Fault Top Depth = 2.2 km). The synthetics were computed at a dense grid of 144 virtual receivers located around the fault up to R jb distance of 100 km. In addition, synthetics waveforms were also simulated for 8 near fault accelerometric stations. For all simulations, a normal fault-plane embedded in a 1D propagation medium with bedrock surface condition was assumed. On the fault, 54 different rupture models were simulated varying the source kinematic parameters such as: i) position of the nucleation point, ii) rupture velocity, and iii) final slip distribution. The synthetic dataset is composed of three groups of more than 10000 simulated accelerograms, each of them corresponding to three different finite-fault simulation techniques (EXSIM, DSM and HIC codes). Data dissemination. The synthetics are distributed as ASCII files, whose name contain the information on the virtual grid of receivers, the site code, the type of simulation, the site conditions, and the ground motion component . The ASCII files contain a header of 55 rows, where the main information describing the synthetic waveforms are included (hypocentral location, magnitude, simulation technique, frequency range, etc.), being followed by a column with ground motion amplitudes. Prior to uploading into the SYNTHESIS database, the synthetic data are processed adopting different standard procedures depending on the considered simulation technique, in order to 39 GNGTS 2013 S essione 2.1