The potentiality of an improved physics-based earthquake simulation algorithm for modelling the long-term spatiotemporal process of strong earthquakes preparation is explored. The physical model on which this version of our simulation algorithm is based includes the Rate & State constitutive law, in addition to tectonic stress loading and static stress transfer. We applied the simulator code to a physical model of the Corinth Gulf (Greece) fault system, a rapidly extending rift about 100 km long, where the deformation is taken by major fault segments aligned along the southern coastline of the Corinth Gulf, and associated with several strong (6.0) earthquakes in the last few centuries. In particular, the recurrence time of strong events and their spatial relation are studied. The results of this simulation provide interesting inferences on the spatiotemporal properties of seismic activity in the study area. As the simulator algorithm allows displaying the stress pattern on all the single elements constituting the seismic structure, in this study we have focused our attention on the time evolution of the level of stress before, during and after strong earthquakes. In particular, we have quantitatively recognized that the ratio between the average stress and its standard deviation on the patches constituting a specific fault segment, always increases at an accelerating rate before a large rupture on a part or the entire segment, or even several collective segments.

A newly developed physics-based earthquake simulation algorithm was applied to a seismogenic model in the Central Apennines Region. This model was derived from the last version of the Database of the Individual Seismogenic Sources (DISS), from which 54 seismogenic faults have been recognized. This simulator allowed the compilation of a synthetic seismic catalog lasting 100,000 years, and containing more than 300,000 events of 4.0

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).