Abstract: Acoustic emission (AE) technique was employed to measure the AE signals of granite for three-point bending tests and shear tests. The spatial-temporal distributions of various fractures micro-cracks were studied based on the simplex locating algorithm and moment tensor theory. The results showed that the micro-cracks generated from the three-point bending tests are mainly of tensile type， accounting for more than 50% of the total events. For the shear tests， the micro-cracks of shear type are prominent whose proportion is more than 60% with rock failure. Moreover， the results of the distribution of AE locations and moment tensors are in agreement with the macroscopic fractures at the end of the experiments， which can be used to describe the distribution and migration of tensile and shear stress when rocks are under loading. The results indicated that the moment tensor theory is a very useful method for studying AE source mechanisms and spatial-temporal vibrations of micro-cracks.

Key words: rock failure, acoustic emission (AE), moment tensor, source mechanism