Non-Local Triggering in Rock Fracture

Combining multiphysics observations in the laboratory, we present novel phenomena for the analogue between rock fracture and seismicity. We show, for the first time in a laboratory setting, how a large-scale flaw in rock can facilitate non-local triggering-remotely triggered damage in rock mass. Results prove analogues of rock fracture evolution to natural seismicity including several lab-analogues on seismicity model predictions beyond power law. We observe under specimen-scale criticality a relatively small AE perturbation occurring at a seemingly random location can trigger cascading events whose spatial span can traverse the entire rock fracture system. The inclination angle of the non-local triggering pairs shows dependence on the large-scale flaw, and the subsequent generations of triggered AEs by these non-local triggers decline significantly slower than that of the general triggers. The rock fracture system evolves to a state where the resistance to non-local triggering continuously reduces, bridging the gap between an idealized lab setting and a natural fault. The non-locally triggered events can also be reactivated as the rock fracture system evolves towards increased complexity. These lab-observations as well as the understanding on the analogue relationship between rock fracture and seismicity may shed new light on the insight of the periodical, dynamic, and unpredictable nature of the multiscale rock fracture process.