Induced and endogenous acoustic oscillations in granular faults

Abstract

The frictional properties of disordered systems are affected by external perturbations. These perturbations usually weaken the system by reducing the macroscopic friction coefficient. This friction reduction is of particular interest in the case of disordered systems composed of granular particles confined between two plates, as this is a simple model of seismic fault. Indeed, in the geophysical context frictional weakening could explain the unexpected weakness of some faults, as well as earthquake remote triggering. In this manuscript we review recent results concerning the response of confined granular systems to external perturbations, considering the different mechanisms by which the perturbation could weaken a system, the relevance of the frictional reduction to earthquakes, as well as discussing the intriguing scenario whereby the weakening is not monotonic in the perturbation frequency, so that a re-entrant transition is observed, as the system first enters a fluidized state and then returns to a frictional state.

Statistical physics of fracture and earthquakes

“…In [34], the remote triggering of seismic activities is addressed from the numerical model of a confined granular medium, representing the gouge layer found in faults, or separating plate boundaries. The so-called fluidization at the resonance frequency of the gouge causes remote triggering of earthquakes.…”

“…The mechanism for such a process is debated. One explanation comes from the just-mentioned fluidization mechanism and the subsequent segregation of the grains due to the Brazil nut effect [34]. Such an effect requires a significant porosity of the system and gravity.…”

Multiscale effects caused by the fracturing and fragmentation of rock blocks during rock mass movement: implications for rock avalanche propagation

“…10e). Then, sliding may occur as the shear stress remains unaltered, and the normal stress carried by the force chain suddenly decreases (de Arcangelis et al, 2018).…”

Collective drifts in vibrated granular packings: the interplay of friction and structure

“…Introduction.-Vibrofluidized granular systems are ubiquitous in industrial applications and geophysical problems [1][2][3][4], and provide a test-ground for theories of nonequilibrium fluctuations [5]. As in many out-ofequilibrium steady states, shaken granular media display correlations which would disappear at equilibrium, for instance between velocities of different particles [6].…”