Spontaneously evolving intermittent shear fractures reproduce the fault formation and isolated earthquake sequence

When a system is subjected to continuous loading beyond its critical threshold, intermittent energy release events occur. Such behavior is observed in systems that span a wide range of temporal and spatial scales. Here, we propose a unique offset-compression loading system based on AZ31 magnesium alloy capable of spontaneously evolving intermittent shear fracture events. The intermittent fractures spontaneously evolve into a self-organized critical state characterized by avalanche-like shear fracture events. In addition, this system enables the coupling of fault formation and seismic events within the framework of an intermittent shear fracture process with spontaneous shear band nucleation. During individual shear fracture events in the magnesium alloy, this system is found to replicate the formation initiation and slip characteristics of both reverse and strike-slip fault systems. By measuring the energy release, we further show that the concentrated energy release during intermittent shear fracture is consistent with the seismic energy release pattern of the isolated earthquake sequence.