Peculiarities of Dynamic Slip Nucleation in a Thin Granular Layer

Abstract—Granular media determine the dynamics of many natural systems including faults in the Earth’s crust. The paper addresses the laboratory study of shear deformation of a model fault simulated by a layer of granular material located between rock blocks. A model fault is a complex dynamic system characterized by the presence of bifurcations and fast and slow slips may take turn aperiodically during deformation. The sliding of the rock blocks is accompanied by the generation of acoustic emission pulses (AEs) which are identified based on the Akaike information criterion. The dynamics of AEs reflects the evolution of mechanical properties of the fault. In the flow of AEs, the subsets with different rise time/amplitude values (RA-values) and different scaling relations are identified. Applying the random forest machine learning algorithm to the analysis of AE catalogue demonstrates the possibility of determining the velocity of fault sliding and the time to both fast and slow slips. The nucleation of a certain slip mode is predetermined by the self-organization processes taking place in the central zone of a fault, and the characteristics of the AE reflect these processes. The proposed approach to the estimation of fault sliding parameters can be promising for the design of new methods for monitoring stressed massifs at mining.