摘要
断层活动导致断裂带裂隙广泛发育,成为地壳中流体运移与聚集的有利通道和场所.流体在地震过程中具有重要作用.流体与地震破裂带内的岩石相互作用导致其具有与其他完整岩石不同的性质,包括矿物-化学组成、粒度分布及传输性质(渗透率、孔隙度)等.这些特性可以视为流体与地震断层带岩石相互作用的响应.一方面,较高的孔隙流体压力导致断层的有效正应力降低.另一方面,流体会与断层岩发生一系列水-岩反应导致矿物蚀变、分解,生成大量摩擦系数较低的粘土矿物,同时一些不稳定元素可能会随流体发生迁移,导致大量物质流失.在地震周期过程中,伴随着流体运移,断层带的物理性质(渗透性、流体压力等)也随之发生变化.同震快速摩擦生热会导致流体产生热压作用,促进同震滑动.另外,同震破裂导致断层带的渗透性快速上升,较高的流体压力会很快释放.在间震期过程中流体会使破裂趋向于缓慢变形,矿物溶解-沉淀、重结晶及压溶等作用胶结并愈合裂隙,断层强度恢复的同时断层带渗透性逐渐降低,孔隙压力又逐渐积累.研究流体的这些物理化学行为对理解地震成核、同震滑动及震后断层愈合等过程有重要意义.本文介绍了有关流体对断层带物理化学性质的改造及流体的动力学意义等方面的研究进展,总结了流体在地震周期过程中所产生的一系列岩石物理化学效应及其对地震过程的影响.
Seismic faulting commonly produces extensive fractures and leads to the fault zone serves as apreferential agent for fluid migration in the crust.These trapped fluids in fault zone may play key roles during faulting processes.Extensive fluid-rock interaction results in distinct rockproperties characterizing fault rocks,including their mineral and geochemical compositions,grain size distributions,and transport properties（permeability,porosity）.These features are taken as responses of fluids acting on fault rocks during seismic cycles.On the one hand,high pore fluid pressure can significantly reduce the effective normal stress.On the other hand,the mineral alterations and element diffusion caused by fluid infiltration drive mass transfer and produce low strength clay minerals.Fluids may play various roles in different stages of seismic cycles.Co-seismic frictional heating elevates the temperature of fluids rapidly and leads to thermal pressurization.Moreover,co-seismic fracturing and dilatancy can significantly increase the permeability of fault zone and consequently lead to the leakage of pore fluids that accumulated before fault slip.During the long term inter-seismic periods,the penetrated fluids passing through fault zone react with crushed fault rocks, dissolving and transporting mobile elements away.Meanwhile,with the cementation and healing of cracks by dissolution-precipitation,recrystallization and pressure solution,the permeability of fault zone will be concomitantly reduced,and pore pressure will be reasonably built up.Therefore,study on these physico-chemical behaviors of fluids in seismogenic fault zone is important in understanding the earthquake nucleation,co-seismic slip and post-/interseismic fault healing processes.This paper summarizes these effects of fluids on fault zone structures,compositions and transport properties as well as the dynamic effects of fluids on fault zone evolutions.
出处
《地球物理学进展》
CSCD
北大核心
2015年第6期2448-2462,共15页
Progress in Geophysics
基金
中国地震局地震行业科研专项(201508018)
国家自然科学基金(41372202
41102130)
地震动力学国家重点实验室自主研究课题(LED2010A03)联合资助
