【摘要】 在实验室利用分布式多通道瞬态信号采集系统,从近场条件下研究了岩石粘滑过程中沿断层的声发射信号的初动到时和初动方向空间分布,并结合瞬态高频应变记录系统观测沿断层的应变分布特征,对粘滑过程中的震源错动行为进行了研究。实验在双轴伺服加载系统上进行。分析表明,一次突发应力降对应的瞬时震源滑动过程是由多次更短暂的微小错动组成的,每次短小错动都产生自己的声发射事件,并依次对应不同的应变值快速改变。而每一次的微小错动也可能不止一个位错点,而是对应空间上多个启动点,从振动波初动信号的空间分布形式与沿断层应变场不均匀分布中可以找到证据。近场条件下观测到的粘滑过程多点错动现象对于理解震源过程的复杂性,解释现场地震震源不确定性与震源机制解的高矛盾比现象提供了可能的依据。更多还原

【Abstract】 By using a newly developed distributed multi-channel transient signal acquisition system,the spatial distribution of arrival time and direction of the first motion of the acoustic emissions(AE)along the fault under near field conditions was well studied. With the high frequency strain recording system,the stress distributions along the fault were well characterized and the focal dislocation behavior during stick-slip was studied as well.The experiment was conducted in a biaxial servo-control loading system. Analysis shows that for each sudden stress drop event,the corresponding focal dislocation consists of a few smaller sub-dislocations and each sub-dislocation results in its own AE event and stress change. Besides,it can be proved that each sub-dislocation may correspond to multiple sources rather than point source,the evidences of which can be found in the heterogeneity of the spatial distribution of the first motion and the strain field along fault. Our study indicates that the multi-dislocation during stick-slip under near field conditions is very complicated. By the result of our study,it is more convenient to understand the complication of focal process. Besides,it could provide an evidence for the uncertainty of in-situ earthquake focus and the high contradiction rate of earthquake mechanism solutions.更多还原