The model experiments that simulate shear slip of preexisting fracture have been conducted under a confining pressure condition in order to investigate
the controlling parameters of "aseismic" fracture. In this paper, we discuss the normal stress and the slip velocity as the possible controlling parameters of AE (Acoustic Emission) occurrence and efficiency. The effects of these parameters on AE activity are investigated through the observation of AE events associated with the stable slip of artificially prepared fracture planes, which are made using split rock specimens. The AE activity during stable slip was evaluated as AE event rate and m-value for statistical evaluation. It has been suggested that the normal stress acting on the fracture plane has less effect on AE event rate and m-value, and that slip velocity has negative effect on AE event rate as well as m-value. The mechanism of the effect of normal stress is explained with the normal stress insensitivity of surface contact condition on the fracture, while the effect of slip velocity has not yet been clarified.

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