断层带流体对断层强度和强震孕育的影响

大量研究表明,流体在断层弱化中起着非常重要的作用.在地壳浅部脆性域,自由水通过流体孔隙压力减小断层有效正压力,从而降低断层摩擦强度;在地壳深部,矿物中的微量结构水弱化岩石流变强度.另外,流体-岩石相互作用等化学过程,如长石水解反应,对断层强度的影响也非常显著.断层深部流体通过物理作用与化学作用影响着岩石的变形机制,从而影响断层力学性质与地震孕育和发生.断层内部流体孔隙压力周期性变化是断层带脆-塑性转化、裂缝张开与愈合等的直接体现,这种变化控制着断层强度与强震周期性发生现象.

Effect of the fluid to fault strength and strong earthquake gestation

Fluid plays a very important role in weakening behavior of fault. In the shallow crust with brittle deformation, the pore fluid pressure from water decreases effective normal pressure and friction strength of fault. In the deep crust, the trace structure water in minerals weakens rheological strength of fault. Besides, fluid-rock interactions, especially the chemical process, such as feldspar hydrolysis reaction, have a significant influence on fault strength. The fluid in the deep fault zones affects the deformation mechanism through the physical and chemical action, which controls fault mechanics properties and earthquake gestation. The periodic changing of pore fluid pressure in fault zone is the reflection of brittle plastic transition, fractures opening and healing. These processes control the fault strength, and lead to strong earthquakes occur periodically.