| Summary: | Three successive instabilities are generated in a progressive shear-sliding failure under uniaxial compression. These instabilities show the distinctive acoustic emission (AE) features that display strong similarities with stick-slip experiments on core specimens. However, detailed AE and optical analyses reveal the differences: (1) AE features are divided into two groups: fault-development and fault-slip. The former is similar to AE features from an intact rock, while the latter is similar to tectonic-scale seismic activities; (2) optical observations display a series of phenomena that also can be categorized as: fault-development includes fault initiation, its widening and fully-development, off-fault crack development; fault-slip involves creation and growth of marble powder gouge in the fault, and migration of brightening grains along the fault. Thus, the discovery from the study is the first and second instabilities are two different stages during the fault-development, and only the third instability represents the actual stick-slip along a well-formed fault.
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