Fault-rock analysis of spatial fixed initial break point, the case study in landslide area

在实验室的岩石摩擦试验中，已经观察到特定地点的破裂成核，地震观测已经识别出大地震的空间固定的初始断裂点，但这种空间固定的原因仍然不确定。滑坡是一种中等规模的岩石摩擦事件，介于小型试件的实验室压缩实验和孕震断层之间。所研究的滑坡区是一个在降雨过程中发生幕式滑动的孔隙流体诱发的正断层系统。在滑动过程中监测了HIS断裂系统的动力学过程，并分析了滑动事件发生后第一个断裂点的断裂点。在地下水位较高的地区发生膨胀和滑动，破裂扩展到周围。2003年和2004年多次发现了类似的过程，两年都是在同一地区开始破裂的。摩擦非均质性似乎在空间上是固定的，并可能取决于水文结构。在初始破裂点，在低渗透泥层下的裂隙带中发现了高含水率。裂隙带可能起到输送流体的作用，而源自剪切研磨的断层泥可能已经封闭在孔隙流体中，造成了高流体压力。随着滑移系统的成熟，历史断裂岩的发育和随后形成的水文结构可能会达到静止状态，导致反复滑动事件的初始断裂点在同一地区。

The nucleation of rupture at a specific site has bee observed during rock frictional testing in the laboratory, and a spatially fixed initial break point has been recognized for large earthquakes by seismic observation, but the cause of this spatial fixation is still uncertain. A landslide is a midscale rock-friction event, in between a laboratory compressional experiment on a small test piece and a seismogenic fault. The landslide area studied is a pore-fluid-induced normal fault system that udergoes episodic slip during rainfall events. we monitored dynamic processes of his fault system in detain during slip and analyzed the fault rock at the initial break point immediately after slip events. Dilation and slip were initiated in an area with a high groundwater level, and the rupture propagated into the surrounding. A similar process was recognized repeatedly in 2003 and 2004, and the rupture initiated in the same area both years. The frictional heterogeneity seems to be spatially fixed and may depend on the hydrologic structure. At the initial break point, a high water content was found in a fracture zone under a low-permeable gouge layer. The fracture zone may act as a conduit for fluid, and the gouge, which originated from shear grinding, may have sealed in the pore fluid, causing high fluid pressure. Historical fault-rock development and the consequent hydrologic structure formed may reach a stationary state with maturation of the slip system, causing the initial break point of repeated slip events to be in the same area.