Effects of heterogeneity in rock samples on spa tial and temporal distribution of acoustic emission and their significance in se ismology
标本非均匀性对岩石变形声发射时空分布的影响及其地震学意义

Based on a set of experimental results, the effects of heterogeneity (pre existing microcracks and macrostructures) in rock sample on spatial and temporal distribution of acoustic emission (AE) were discussed. The comparative analysis indicates that the existence of pre existing microcracks makes AE occurrence rate rapidly increase prior to the fracture nucleation. In addition, the b value shows a short term anomaly, i.e . fluctuation on a decreasing background, which increases the predictability of the fracturing time. The effects of pre existing macrostructures, such as joint, bedding plane on AE occurrence rate and b value are the same as that of microcracks. AE spatial distribution is controlled by the pre existing macrostructures and the macrostructure clustered by AE events usually controls the coming final fracture. This means that the existence of macrostructures makes prediction of the time and location of the final fracture possible.