Laboratory-derived friction data for sandstone samples
Description
The stress anisotropy in the Earth’s crust is a crucial factor in seismic mechanisms, however, its role in controlling frictional properties and slipping stability of faults remains poorly constrained. Here, we conduct velocity-stepping experiments on sandstone under true triaxial stresses by varying σ2/σ3 ratios and σ3 within the rate-and-state framework. The results show that elevating stress anisotropy by increasing stress σ3 at the constant σ2/σ3 ratio leads to a decrease in frictional strength. Using the Coulomb failure criterion, the friction angle decreases and the cohesion increases exponentially with increasing σ2/σ3 ratio. The fault stability, as determined by the frictional velocity-dependent parameter (a-b), decreases with increasing stress anisotropy, which is characterized by a transition from velocity-strengthening to velocity-weakening behaviors. The enhanced fault critical stiffness (Kc) with increasing stress anisotropy could promote fault instability nucleation by reactivating local aseismic faults in seismogenic zones. We further study the laboratory fault surface evolution and find that shallow grooves are generated that act as stress barriers at low geologic stress anisotropy. As the geologic stress anisotropy increases, the fault surface gradually converges to uniform smoothness due to the abrasion of asperities. These results suggest that the weakening effect of stress anisotropy on fault stability is associated with stress redistribution produced by shear localization. The excessive stress anisotropy can alter the frictional behavior of slow slip or aseismic creep, potentially inducing earthquakes. This dataset contains the raw data from friction experiments performed on sandstone samples. Taking S-2-6-3 as an example in sample numbering, where S represents the sandstone sample, 2 indicates the ratio of the intermediate principal stress to minimum principal stress (σ2/σ3), 6 represents the intermediate principal stress σ2 and 3 denotes the minimum principal stress σ3.