Abstract: We have performed a series of frictional experiments using a servo-controlled biaxial loading machine with three granodiorite block direct shear configuration.In the experiments,a small-amplitude sine wave of displacement is modulated to shear loading to study the effects of shear stress perturbation on stick-slip instability.The main results are as follows.Under constant normal stress and constant loading point velocity in shear direction,the sample shows regular stick-slip behavior.After the displacement perturbation is modulated to shear loading,the correlation between the timing of stick-slip and the perturbation increases as the perturbation amplitude increases.Stress drop and interval time of stick-slip events also tend to be scattered,and the critical amplitude for producing significant impact is around 0.05MPa.The tendency that the stress drop and interval time of stick-slip events are scattered with increasing perturbation amplitude is more obvious at higher normal stress,and the correlation between the timing of stick-slip and the perturbation also increases with increasing normal stress at the same perturbation amplitude.The effect of perturbation period on friction is not evident.The results imply that the change in Coulomb shear stress caused by strong earthquake may obviously change not only the occurrence time of earthquakes but also the earthquake magnitude on nearby faults.

Key words: frictional experiment, stick-slip, stress perturbation, stress drop, interval time of stick-slip events

摘要： 利用双轴伺服控制加载装置,采用3块花岗闪长岩标本组成的含有2个滑动面的直剪结构,开展了摩擦滑动实验。实验中通过在剪切方向上叠加正弦波状的位移扰动,研究了剪应力扰动对断层粘滑失稳的影响。研究表明,在恒定的正应力和位移速率下,标本表现出较为规则的粘滑;当在剪切方向叠加位移扰动后,随扰动振幅的增加,粘滑发生时间与扰动的相关性增大,粘滑的应力降和时间间隔的分布趋于离散,其中扰动能产生明显影响的临界振幅大致为0.05MPa;粘滑应力降和时间间隔随扰动振幅增大而逐渐离散的现象在较高正应力下更为明显,而相同扰动振幅下粘滑失稳发生时间与扰动的相关性也随正应力增加而增大;扰动周期对摩擦性状的影响不明显。研究结果意味着,地震引起的同震剪应力的变化不仅会引起邻近断层上地震发生时间的变化,也可能引起地震强度的变化。

关键词: 摩擦实验, 粘滑, 应力扰动, 应力降, 粘滑间隔