Speaker
Description
The organization in time, space and energy of earthquakes exhibits scaling laws with exponents $\alpha,\beta,\gamma$ and $p$
which are universal, i.e. they are independent of time and of the geographic region.
A possible explanation of this critical-like behavior is provided by the possibility to describe the evolution of a seismic fault
under friction within the general context of the depinning transition. In fact, minimal models for the seismic fault, such as the Burridge-Knopoff model, can be mapped to classical quenched Edwards-Wilkinson (qEW) interfaces. Nevertheless the exponents of the scaling laws
of the qEW interfaces are different from those exhibited by instrumental earthquakes.
In this talk I will present a more realistic description of the seismic fault which can be viewed as a qEW interface evolving over
a viscous-ductile substrate. I will show that this description produces scaling laws with exponents $\alpha,\beta,\gamma$ and $p$ in very good agreement with experimental values. More precisely, the values of the exponents $\alpha,\beta$ and $\gamma$ are quite independent of model parameters and this explains their universal character. Conversely the exponent $p$, controlling the temporal clustering of seismic sequences,
depends on the specific law implemented for the viscosity. The value $p=1$ of instrumental data is recovered assuming a velocity-strengthening law for the viscous layer, which is a quite realistic description of real fault systems.
