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21.
Weakening of a prestressed sawcut in Westerly granite under laboratory condition is accomplished by injecting pressurized fluid into the sawcut. After injection a sequence of stick-slips is observed while the deviatoric stress decreases successively with each stick-slip. On the basis of the experimental observation we develop a model of fault instability due to inhomogeneous and progressive weakening of the fault. According to this model, the fault surface is divided into the slipped and the locked regions, depending on whether or not the local state of stress satisfies the friction criterion. The average shear stress in the slipped region decreases with time and, in order to maintain a quasi-static equilibrium, shear stress in the remaining locked region on the fault surface increases. This situation may last until a critical state of stress on the fault is met, at which a sudden instability (stick0slip) may occur. We suggest that this mechanism of stress transfer may be a viable mechanism of induced seismicity and aftershocks, in addition to the well-known mechanism of a local increase of pore pressure. By comparing the experimental data with model predictions we show that the critical condition for slip instability is when the average shear stress over the locked region becomes equal to the value given by the friction criterion. Thus the friction criterion established for slip on fractures on which the state of stress is macroscopically uniform may also be applicable to fractures on which the stress state is macroscopically heterogeneous. 相似文献
22.
通过基于“瞬间闭锁”假定的多滑块-弹簧模型对摩擦滑动进行模拟,讨论了强度分布不均匀性及系统刚度构成对整个系统稳定性的影响.通过图示平均剪应力和平均位移的关系,对断层模型随错动的演化作了清晰的描述.结果表明:(1)均匀的滑动面及外部系统刚度较小的情况(这相当于高压条件下形成的光滑剪切破裂面的情况)易于发生粘-滑振荡.(2)随着错动次数的不断增加,错动的空间分布向不均匀方向发展,从而使平均应力降减小,系统整体趋向稳定,即断层活动历史越长越趋向稳定.(3)由于导入了具有负刚度效果的力和位移组合控制,通常加载方式条件下只能产生不稳定的过程可以转变为一个平均效果上的准静态弱化过程,类似于滑动弱化过程. 相似文献
23.
黏滑断层隧道减错措施参数对减错效果的影响分析 总被引：2，自引：1，他引：1
为提高黏滑断层隧道的结构安全性和稳定性,对黏滑断层隧道设置不同缝宽减错缝、不同刚度减错层的减错效果进行研究。研究结果表明:断层黏滑错动对上盘隧道的影响远大于下盘;减错缝对上盘部分隧道结构的减错效果优于下盘,其中上盘减错效果最大为24.50%,下盘减错效果最大为9.26%;减错层对下盘部分隧道结构的减错效果略优于上盘,其中下盘减错效果最大为105.32%,上盘减错效果最大为78.07%;随着减错缝宽度的增加,隧道上盘减错效果变好,下盘缝宽10—15cm减错效果最好;随着减错层弹性模量的增加,隧道上下盘减错效果降低,当减错层弹性模量增加到一定程度（约100MPa）,减错效果趋于稳定。研究成果可为黏滑断层隧道的减错结构设计及施工提供参考。 相似文献
24.
本文以永胜地震台FSQ型浮子水管倾斜仪原始记录图形为基础,介绍了澜沧-耿马大震前后的地形变特征,探讨了大震破裂的前后过程。这些珍贵的原始记录图型,对今后该区7级以上大震的短临预报可能具有重要的参考价值。 相似文献
25.
The faiture of pre-existing faults was studied experimentally and theoretically. The stress concentration around open and healed slits in plexiglas under uniaxial stress was calculated and compared to observations by Schlieren photographs. The rupture velocities along these pre-existing faults were found to vary from 0.25 of the shear velocity up to velocities slightly exceeding the shear velocity. Sudden fault dislocation was often preceded by stable sliding. The amplitudes of elastic waves radiated in the forward quadrant of the rupture were larger than the amplitudes in the backward quadrant. 相似文献
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本文通过三种结构模型的黏滑地震模拟实验,利用高频速度连续观测系统获得了地震失稳过程的速度特征,讨论了最大位移量的选取方法,估算了实验室黏滑型地震的矩震级,探讨了黏滑类型、应力降大小与震级的关系.结果表明,黏滑型地震的应力降过程可能包含一次到多次高频振荡,对应若干次黏滑子事件.高频振荡的摆动幅度很大,包含有多种频率成分,峰值速度0.003~0.008 m·s-1.初步估计黏滑型地震的震级范围为-4.4~-3级,断层构造面的差异对各种黏滑模型的地震震级分布有明显影响.总体来看应力降与地震震级没有明显相关性,决定地震震级的主要因素应当是震源尺度. 相似文献
27.
利用双轴伺服控制加载装置,采用三块花岗闪长岩标本组成的含有两个滑动面的直剪结构,开展了摩擦滑动实验.实验中通过在垂直滑动面的载荷上叠加正弦波状和方波状的扰动,研究了正应力扰动对断层黏滑失稳的影响.研究表明,在恒定的正应力和位移速率下,标本表现为规则的黏滑,叠加正应力扰动后,随扰动振幅的增加黏滑发生时间与扰动的相关性增大,黏滑应力降和时间间隔的分布趋于离散.黏滑应力降和时间间隔的平均值随平均正应力的增加呈线性增长,扰动叠加后黏滑应力降的离散度随平均正应力的增加而增大;黏滑应力降和时间间隔主要受应力变化幅度的影响,而与应力变化的速率关系不大.剪应力和正应力扰动都会对断层黏滑失稳产生影响,而正应力扰动的影响更明显.这两种扰动对断层黏滑失稳影响的机制存在差异,剪应力扰动只是改变断层滑动的推动力,而正应力扰动则改变了断层面上凹凸体的接触状态. 相似文献
28.
实验研究断层黏滑过程的变形演化,尤其是失稳黏滑瞬间的断层位移演化特征,对于了解地震从孕育到发生的全过程具有重要意义.本文基于数字散斑相关方法(digital speckle correlation method, DSCM),用三套图像采集系统(两套低速和一套高速图像采集系统)搭建了断层黏滑过程的多观测区域、多时间尺度的变形场测量系统,并用此系统对一种花岗岩双剪滑动模型的黏滑过程进行了实验研究.对间黏滑期和黏滑期断层位移演化特征进行深入分析的结果表明:间黏滑期断层位移演化体现出空间上的非均匀性和时间上的"趋同化"特征,断层滑动趋同化也许是断层错动匀阻化的一种宏观表现形式;断层黏滑动态过程持续时间非常短(本文300 mm断层黏滑过程持续时间约在1 ms量级),黏滑失稳前会出现预滑,预滑出现到黏滑失稳发生所经历的时间与黏滑失稳过程所用时间相差一个量级;断层的一次黏滑由若干个滑动速度不同的、小的失稳滑动组成,黏滑失稳过程中断层的滑动速度呈现出波动性,整个滑动过程中断层经历了多个高速滑动和低速滑动的交错. 相似文献
29.
With the more complete acoustic emission (AE) catalog improved by the multi-channel AE matched-filter technique (MFT), we study the spatiotemporal evolution of the AE activities after laboratory stick-slip events incorporate with the slip data recorded by displacement transducers on an ~1.5 m granite fault. The results show that the number of the AE events identified by MFT is about 9 times larger than that of the traditional method. A logarithmic expansion of early AE events along the fault strike is observed as a function of time, whereas the fault does not slip in the same manner. Thus, we related the expansion of the early AE events along the fault to the stress transfer caused by the adjacent AE events. Moreover, there is a good correlation between the cumulative number of the later AE events and the amount of fault slip. It suggests that the stress change caused by the continuous slip of the simulated fault after the stick-slip events response for the later AE events near or on the simulated fault. 相似文献
30.