关键词: 摩擦实验, 应力扰动, 粘滑间隔, 应力降

Abstract: The crustal movement shows obviously non-linear characteristics in time and space,and the tectonic deformation and related phenomena are undoubtedly affected by such non-linear mechanical process. Experimental study on frictional behavior under non-linear loading is helpful for understanding the effect of stress change on earthquake mechanism. In this paper,the frictional experiments on medium-scale granodiorite samples containing 45? precut surface have been conducted by using a servo-controlled biaxial rig,and the effect of lateral stress (σ₂) on friction has been studied. The experimental results indicate that the interval and stress drop of stick-slip events increase with increasing normal stress on sliding surface under constant loading velocity in the direction of maximum compression stress σ₁ and constant lateral stress σ₂.However,the relation is greatly changed when stress perturbation of sine wave with high frequency and small amplitude is added to σ₂. Stress drop and interval of stick-slip events are obviously scattered. In particular,the magnitude of stress drop may tremendously increase. Strain measurement indicates that the perturbation of lateral stress increases the heterogeneity of strain distribution and release along fault,and stick-slip events with large stress drop and that with small stress drop are corresponding to strain release along whole fault and that along parts of fault,respectively. Compared to the previous experiment result of stress perturbation in σ₁,the effect of perturbation in σ₂ on stick-slip is more obvious,meaning that change in normal stress may affect fault instability more greatly than change in shear stress. The experimental results imply that not only the effect of change in coseismic Coulomb stress on seismicity should be analyzed,but more attention should be paid to the possible effect of change in normal stress on fault when the fault interaction is considered.

Key words: Frictional experiment, Stress perturbation, Stick slip, Stress drop