<p>Numerous rockbursts induced by geological heterogeneities, particularly structural planes and faults, pose significant risks during tunnel excavations. These events seriously threaten the safety of construction personnel and equipment. To investigate the evolutionary instability mechanism of fault rockburst induced by a structural plane, this study focuses on multiple successive intense rockbursts in a deep drainage tunnel using microseismic monitoring. By examining the spatiotemporal evolution of microseismic activity, this study systematically records the nucleation and development of an extremely intense rockburst and identifies the potential structural plane and responses of microfracture precursor. Variations in seismic source parameters—including microseismic energy, event density, cumulative apparent volume, energy index,and <i>E</i>_S/<i>E</i>_P ratio were analyzed to further elucidate the failure process and evolutionary mechanisms of fault rockburst in deeply buried tunnels. The results indicate that the destruction and development of the fault rockburst can be divided into five stages: fault activation and stress manifestation, stress buildup and shadow, energy accumulation, quiescence, and fault-slip and instability. Fault rockburst are primarily governed by tensile failure, accounting for 80.2% of total microseismic events, whereas shear failures constituting a minority. As rockburst development progresses, the proportion of tensile failures decreases whereas shear and tensile-shear mixed failures relatively increase. Strong shear events with <i>E</i>_S/<i>E</i>_P ratios exceeding 30 are primarily concentrated along and associated with shear slip on structural plane, eventually forming an evolutionary process of tensile accumulation → shear instability. These findings provide a direct case study that serves as a reference for understanding the failure mechanisms of similar rockbursts in deeply buried tunnels.</p>