关键词: 矩张量反演, 巴西劈裂, 加权最小二乘, 聚类分析, 震源机制

Abstract: To study the process and mechanism of rock tensile failure, the advantage of weighted inversion method in solving moment tensor of Brazilian splitting test is first verified by simulation calculation. Acoustic emission monitoring, event location and moment tensor inversion are performed during the Brazilian splitting test on granite, and the difference of moment tensor results between standard inversion method and weighted inversion method is analyzed. Then the moment tensors inverted by the weighted inversion method are analyzed by the K-means clustering algorithm. The results show that the weighted inversion method can reduce the moment tensor inversion error of Brazilian splitting test. In the laboratory granite Brazilian splitting test, the weighted inversion method greatly optimizes the distribution of the double couple component and pressure/tension axis of the acoustic emission event, which makes the inversion result more reasonable. For the weighted inversion result, the events selected for moment tensor inversion can be divided into three clusters, and the source type, stress state, focal mechanism, radiation pattern of events in the same cluster are similar. There is no significant difference in the occurrence time and position of events in different clusters, but in the later stage of the test, events with obvious tension characteristics in the east-west direction increase sharply and gather near the center of the disc and then dominate the whole rupture, which eventually leads to the split of the specimen. The results reasonably explain the failure process and mechanism of the Brazilian splitting test on granite, and can provide further guidance for the study of rock mechanical behavior.

Key words: moment tensor inversion, Brazilian splitting test, weighted least squares, cluster analysis, focal mechanism