Revisiting scale-invariant dynamics in slowly driven systems – ALLSIZESPLAY

In many different systems including earthquakes, granular faults and subcritical rupture, energy is slowly stored and released by sudden scale-invariant avalanches (SIA). The existence of time clustering and a little memory of past events are also usual features of the dynamics, which, besides the relevance of the cited phenomena, remains poorly understood. The direct application in the past of the formalism of phase transitions to treat SIA, has created links between scale-invariance, criticality and predictability that seem in contradiction with results from today’s experiments and earthquake data. Key open questions include the origin, robustness and parameter dependences of SIA, the explanation of memory effects and time clustering and, quite important, the possibilities of predicting catastrophic events. An original experimental system, based on the slow shear of a granular medium that is capable to reproduce in detail the laws of seismicity, is the core of this project. Having acoustics as a main source of information, this setup is on its way to delivering precious information of the granular structure. Other simpler setups will complement it, bringing a complete description of the dynamics. The results will be analyzed conjointly from physics and geophysics perspectives. The direct comparison with real earthquakes will allow both analyzing the common features of the dynamics and (more challenging) trying to interpret earthquake physics in the light of our experimental results. Theoretical efforts will focus on revisiting the links between scale-invariance, criticality and predictability. By analyzing avalanches in classical critical systems like the Ising model and percolation we will develop analytical tools linking the avalanche distribution to the critical properties of the system, before applying them to other SIA models, where the possibilities of prediction will be also analyzed, and ultimately confronting them with our experimental results.