## 3 Microseismic Evolution Characteristics of Rockburst Formation Process
### Special Types of Rockbursts
#### 3.3.1 Structure-Type Rockburst  
The structure-type rockburst often occurs in cave sections with a fault structure or structural plane development. Under the action of fault or structural plane, the magnitude and direction of the original ground stress vary, which affects the bearing capacity of the rock mass. The rockburst occurs because of the fault slip or shear fracture, which has a wider failure range and can result in a higher level of rockburst. Therefore, many scholars have conducted in-depth research on the influence and mechanism of the structural plane on rockbursts. [PERSON] et al. [11] showed that the stress concentration near the structuralplane is evident, and more attention should be paid to the influence of the structural plane in rockburst monitoring and early warning. [PERSON] et al. [42] studied two extremely strong rockbursts that occurred in the Jinping II Hydropower Station and found that the structure plays a key role in the occurrence of rockbursts. [PERSON] et al. [43] analyzed in detail the action mechanism of the structure on rockbursts under different conditions and divided structure-type rockbursts into fault-slip burst, shear rupture burst, and buckling burst. In addition, many scholars have conducted in-depth studies on the relationship between the seismogenic characteristics of structure-type rockbursts and the evolution of microseismicity. [PERSON] et al. [44] found that the existence of a structural plane changed the evolution mode of microseismicity. Compared with strainbursts, high-energy microseismic events occurred in the early stage of the rockburst process, and the radiation energy of a microseismic event was lower before the rockburst. [PERSON] et al. [17] analyzed the microseismic evolution characteristics of three consecutive strong rockbursts that occurred along the structural plane and obtained some unique precursors for structure-type rockbursts, such as the abnormal aggregation of a large number of microseismic events on one side of the tunnel, high and continuous increase in the energy index (_EI_), sharp increase in the cumulative apparent volume, and continuous decrease in the \(b\) value. [PERSON] et al. [45] analyzed the relationship between the formation characteristics of structure-type rockbursts and the law of microseismic evolution. They proposed a series of rockburst prevention measures based on microseismic monitoring. The above studies obtained different results on the evolution law and formation mechanism of structure-type rockbursts, attributed to the difference in the geostress and occurrence state of the structural plane (occurrence, scale, combination, and surface roughness). In addition, the above researchers only studied the effect of small-scale structures on rockbursts; there are few reports on slip rockbursts due to large-scale structural planes. This type of slip rockburst often has a wider damage range and poses a greater threat to tunnel construction. Because of the heterogeneity of rocks, a large number of microfractures are typically formed before a macroscopic failure. Therefore, by identifying the failure types of the microseismic events in the process of rockburst evolution, the evolution mechanism of the rockburst can be analyzed. [PERSON] et al. [46] used the moment tensor method and energy ratio method to study the fracture types of microseismic events in the process of rockburst formation. They found that in the formation process of a strainburst, the proportion of tensile failure events is \(>\)92.5%, and the average proportions of mixed failure events and shear failure events are 1.2% and 3.7%, respectively. In the formation process of a strain-structure slip rockburst (single structural plane), the proportion of tensile failure events decreased to less than 90%, whereas the proportion of mixed failure and shear failure events increased. In addition, with the increase in the number of structural planes, the proportion of mixed failure and shear failure events increased further. [PERSON] et al.