The application of a physics-based earthquake simulation algorithm to the central Apennines region, where the 24 August 2016 Amatrice earthquake (Mw6.2) occurred, allowed the compilation of a synthetic seismic catalog lasting 100,000 years, and containing more than 300,000 M ≥ 4.0 events, without the limitations that real catalogs suffer in terms of completeness, homogeneity and time duration. The seismogenic model upon which we applied the simulator code, was derived from the DISS 3.2.1 database (http://diss.rm.ingv.it/diss/), selecting all the fault systems that are recognized in the central Apennines region, with a total of 54 fault rectangular segments. The physical model on which the last version of our simulation algorithm is based includes, besides tectonic stress loading and static stress transfer as in the previous versions, also the Rate & State constitutive law. The resulting synthetic catalog exhibits typical magnitude, space and time features, which are comparable with those of real observations. These features include (i) an earthquake magnitude distribution departing from the linear Gutenberg-Richter distribution in the moderate and higher magnitude range, (ii) long–term pseudo-periodicity of strong earthquakes and (iii) short- and medium-term earthquake clustering. We found in our synthetic catalog a clear trend of long-term acceleration of seismic activity preceding M ≥ 6.0 earthquakes and quiescence following those earthquakes. A typical aspect of the observed seismicity in Italy and of the Central Apennines region in particular, is the occurrence of multiple events of M ≥ 5.5 earthquakes close to each other in space and time. A special attention was devoted to verify if the synthetic catalog includes this feature. On this purpose, we applied a specific code written in “Mathematica” to count the number of multiple events contained in a seismic catalog under a quantitative definition, finding that the synthetic catalog contains a large number of multiple events but not as frequently as in the real catalog. Lastly, as an example of a possible use of synthetic catalogs, a ground motion prediction equation was applied to all the events reported in the synthetic catalog for the production of PSHA maps (in terms of PGA).
