ABSTRACT
In this study, we discuss the transient process, steady state property and dynamic motions of an inclined fault with constant minimum principal stress, based on a velocity and history dependent friction law with varying normal stress. Examination of the constitutive equations reveals that there exists an instantaneous response in friction stress to any normal stress change. The steady state value of friction stress in such an inclined geometry is not linearly related to logarithm of velocity as in the constant normal stress case, and the curve shape even depends on the coefficient of friction at the reference velocity. The dynamic stick-slip motion shows features similar to that in the constant normal stress case on the whole, but they are different from each other in the following aspects: 1) in the inclined system, velocity covers about 20 orders of magnitude in the deceleration phase, which is much wider than that in the constant normal stress case, 2) the value of stress drop in the inclined fault is greater than that in the constant normal stress case due to the effect of decrease in normal stress during the slip, 3) a relation between stress drop and load point velocity that is similar to the constant normal stress case may be employed for inferring the parameter B-A of velocity dependence from stick-slip motions in triaxial test, but overestimation may arise if the factor 1−μ μcotφ is not taken into account.
