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Abstract:
The regional tectonic stress and rupture processes near a fault are essential for estimating rock mass stability and understanding earthquake nucleation. In this study, a strike–slip fault analog sample (size: 2 m × 1 m × 1 m) was prefabricated by using cement, gypsum, river sand, putty powder, and borax. Horizontal uniaxial compression experiments were performed to mimic a strike–slip fault with different orientations (15°, 30°, 35°, 45°, and 60°). Embedded strain cubes (each with a side length of 30 mm, made of polyurethane with three sets of mutually perpendicular strain rosettes) close to the fault tips and the acoustic emission (AE) technique were used to monitor rupture behavior. The faulting process was divided into four stages: primary stage, steady-state creep, accelerating creep, and post-earthquake creep. The fault orientation substantially affected the variation range of local stress deflection angle in dilatation quadrants from −30° to 30°, and in the compression quadrants from −30° to 0°. A larger fault orientation increased the likelihood of a mixed failure mode dominated by shear. The highest correlation between the absolute change of the local stress deflection angle and the AE event count rate was observed during steady-state creep, and the relationship was well fitted by Boltzmann function. The 35° fault shows the strongest rupture activity before the earthquake occurrence. A simple shear model can be applied to explain the faulting process when the fault’s strike is oblique to the direction of applied load.
