The role of driving rate in scaling characteristics of rock fracture

We present the chronological series of acoustic emission (AE) signals detected in samples of Westerly granite loaded in different regimes, one of which included a feedback loop between the axial stress and AE activity. In both regimes, the fracturing system evolves without a characteristic energy scale and with the same scaling exponent independently of the applied feedback. The scaling properties of the waiting-time distribution are more sensitive to both the drive control and the stage of fracture process. The revealed period of a lack of time correlation during continuous loading is explained by the transition between the hierarchic levels in the heterogeneous material.