Physics based models of earthquake clustering

Speaker: Rodolfo Console
“In the last decade, several statistical models for both short-term and long-term earthquake occurrence have been developed and tested, proving a fairly good performance in earthquake forecasting. In particular, a number of studies have considered the ETAS model, for short-term earthquake clustering, and the BPT distribution, among the long-term renewal models. However, statistical models, describing the behavior of large sets of earthquake, fail in forecasting with high reliability the behavior of a single earthquake source.

On the other hand, in the recent years, studies about earthquake mechanics and laboratory experiments on the friction constitutive laws of faults have increased our knowledge of the earthquake nucleation process. Nevertheless, these physical studies allow only simulations of earthquake source behavior, and have never proved predictive capability in real cases.

It is hopeful that the integration of physical and statistical approaches, that up to now have been studied by different groups of seismologists, can improve our ability of describing the earthquake process with the aim of a better predictive capability.

The stress interaction among seismic sources is taken as an example of physical modeling of the earthquake process. This modeling requires two distinct ingredients: (a) the computation of the co-seismic Coulomb stress change produced by slip on a fault, on other faults that can potentially generate subsequent earthquakes; and (b) the Dieterich (1994) rate-and-state constitutive law, as a possible physical justification of the Omori law describing typical aftershock decay.

First, in this presentation I consider the Dieterich’s rate-and-state model as a component that can be included in the ETAS model for the time decay of the triggered events, allowing a substantial reduction of the number of free parameters needed in the purely statistical model. Lastly, an example of a fully physics based model of short-term earthquake interaction with only one free parameter, based on the computation of the Coulomb stress change, is considered. The application of both models is made on a series of moderate seismic events occurred in Central Apennines (Italy) in 1997.

Related references:

Console, R., Murru, M., and Catalli, F., 2006, Physical and stochastic models of earthquake clustering, Tectonophysics, 417, 141-153.

Console, R., Murru, M., Catalli, F., and Falcone, G., 2007, Real time forecasts through an earthquake clustering model constrained by the rate-and-state constitutive law: Comparison with a purely stochastic ETAS model, Seis. Res. Lett., 78, 49-56.

Catalli, F., Cocco, M., Console, R. and L. Chiaraluce, 2007, Modeling seismicity rate changes during the 1997 Umbria-Marche sequence (central Italy) through a rate- and state-dependent model. J. Geophys. Res., 113, doi:10.1029/2007JB005356.”