横向断层对主断层粘滑扩展过程阻止和滞后作用的实验研究

RESEARCH ON THE EFFECTS OF STOP OR DELAY, WHICH LATERAL FAULTS INFLUENCE UPON MAIN FAULT IN THE UNSTABLE EXTENDING PROCESS OF STICK-SLIP

本文给出了一种带有软弱障碍体的粘滑实验结果.软障碍体由垂直于主断面的孤立锯缝加以模拟.实验表明,这种软障碍体对粘滑失稳扩展有明显的阻止(或称为止裂)和滞后作用.这种止裂或滞后作用依赖于锯口的深度l和施于主断面上的正应力_x.止裂和滞后效果随锯口深度增加,滞后效果并不单调随断面上正应力增加,滞后时间和平均正应力曲线呈V形分布.沿断层的视破裂能G表明,失稳扩展停止或滞后的前方往往不是高能垒,说明破裂的停止或滞后并不单是高能壁垒阻挡一种机制,软障碍体具有另一种止裂机制,它可能是通过对应变能的吸收而起到使失稳扩展停止或滞后.本实验还展示了在粘滑事件之间时空上的复杂图象,如本实验中复合构造格架情况下所见的那样,这对理解强震序列的时空关系会有所启发.粘滑扩展过程的停止或滞后机制的研究将有助于粘滑机制的完善.

The laboratory results of stick-slip of a fault with weak barrier were presented in this paper. The weak barriers were simulated by two isolated saw kerfs which meet at right angles with the sawcut representing the fault. The results show that the weak barriers obviously can stop (or called stop-fracture) or delay the unstable stick-slip extending process. The a stop-fracture effects depend on the depth of the saw kerf and average normal stress which exert on the saw cut representing the main fault. The effects of stop and delay increase with l,and increase with but not monotonously. The average delay time curve is like a 'V' shape. The spatial distribution of apparent fracture energy,G,ploted against distance along the main fault shows that there is no high G in the front of the stop points in the unstable extending process,which indicates that the weak barrier is another stopbreak mechanism. It may stop or delay the unstable extending process of stick-slip by absorption of strain energy. The results show some complex time and space features of stick-slip events under conditions represented in this sample,which can help us undersdand the relation between strong earthquake sequences. Further research on the stop or delay effects of the extending process can help us perfect the stick-slip mechanism in seismology.