Effects of normal stress variation on the strength and stability of creeping faults

摘要: [1] A central problem in studies of fault interaction and earthquake triggering is that quantifying changes frictional strength the constitutive response caused by dynamic stressing. We imposed normal stress vibrations on creeping laboratory shear zones to investigate process weakening conditions under which resonant behavior occurs. Layers quartz powder were sheared at room temperature a double-direct geometry n = 25–200 MPa, vibration amplitude A 0.1–10 period T 0.1–200 s, loading rate V 1–1000 μm/s. Frictional varied systematically with A, T, V. Small-amplitude, short-period had no effect strength, but large-amplitude, reduced zone about 1%. Intermediate periods phase lags between vibrations. During long-period vibrations, sinusoidally, an consistent constant coefficient friction. Our data show friction exhibits critical period, as predicted theory. At long periods, Dieterich (aging) law, Linker modification describe step stress, provides good fit our experimental results for all short however, theory predicts more than we observed experimentally, suggesting existing state laws do not account full physics experiments. normal-force can weaken potentially destabilize steadily zones.