摘要
This study investigated the fault nucleation and rupture processes driven by stress and fluid pressure in finegrained granite by monitoring acoustic emissions (AEs). Through detailed analysis of the spatiotemporal distribution of the AE hypocenter, P-wave velocity, stress-strain, and other experimental observation data underdifferent confining pressures for stress-driven fractures and under different water injection conditions for fluiddriven fractures, it was found that fluid has the following effects: 1) complicating the fault nucleation process,2) exhibiting episodic AE activity corresponding to fault branching and the formation of multiple faults, 3)extending the spatiotemporal scale of nucleation processes and pre-slip, and 4) reducing the dynamic rupturevelocity and stress drop. The experiments also show that 1) during the fault nucleation process, the b-value for AEschanges from 1 to 1.3 to 0.5 before dynamic rupture, and then rapidly recovers to around 1–1.2 during aftershockactivity and 2) the hydraulic diffusivity gradually increases from an initial pre-rupture order of 0.1 m2/s to10–100 m2/s after dynamic rupture. These results provide a reasonable fault pre-slip model, indicating thathydraulic fracturing promotes shear slip before dynamic rupture, as well as laboratory-scale insights into ensuringthe safety and effectiveness of hydraulic fracturing operations related to activities such as geothermal development, evaluating the seismic risk induced by water injection, and further researching the precursory preparationprocess for deep fluid-driven or fluid-involved natural earthquakes. The publicly available dataset is expected tobe used for various purposes, including 1) as training data for artificial intelligence related to microseismic dataprocessing and analysis, 2) predicting the remaining time before rock fractures, and 3) establishing models andassessment methods for the relationship between microseismic characteristics and rock hydraulic properties,which will deepen our understanding of the interaction mechanisms between fluid migration and rock deformation and fracture.
