中文摘要：

野外、实验和地震数据表明：浅部地壳的变形以脆性破裂为主,深部地壳的变形以晶体塑性流动为主。在这种认识的基础上,提出了地壳变形的2种机制模型,即发生脆性变形的上部地壳强度基于Byerlee摩擦定律以及发生塑性变形的下部地壳强度基于幂次蠕变定律。而位于其间的脆塑性转化带的深度与浅源地震深度的下限具有很好的一致性。然而,二元结构的流变模型局限性在于其力学模型过于简单,往往过高估计了脆塑性转化带的强度。问题的根源在于对脆塑性转化带的变形机制的研究已有很多,但没有定量的力学方程来描述脆塑性转化带强度;而且以往对断层脆塑性转化带的研究主要集中在温度引起的脆塑性转化方面,对因应变速率和流体对脆塑性转化的影响方面的研究也比较薄弱。对断层带内矿物变形机制研究表明,某些断层带脆塑性转化发生在相同深度（温度和压力）内,发生脆塑性转化的原因是应变速率的变化,而这种变化被认为与地震周期的同震、震后-间震期蠕变有关,这种变化得到了主震-余震深度分布变化的证实。对断层流体特征分析表明,断层带内可能存在高压流体,这种高压流体会随断裂带的破裂及愈合而周期性变化,在地震孕育及循环中起着关键性作用。高压流体的形成（裂隙愈合）有多种机理,其中,压溶是断层带裂隙愈合的主导机制之一。研究在水作用下的压溶,可以对传统的摩擦-流变二元地壳强度结构及其断层强度进行补充与修正。通过以上分析,认为有必要通过野外变形样品和高温高压实验,深入研究应变速率及流体压力对断层脆塑性转化的影响,同时,通过实验建立压溶蠕变的方程,近似地估计脆塑性转化带的强度。

英文摘要：

Constraints provided by field observation,laboratory experiments and seismic data have lead to a general consensus that the shallow crust deforms by brittle faulting,while the lower crust deforms by crystal plastic flow.These constraints provide the basis for the dual mechanism model for the rheology of the crust and lithosphere in which the strength of the upper brittle crust is limited by Byerlee＇s law,while the strength of the lower ductile crust is limited by power law creep.The maximum depth of microseismic activity is controlled by the broad zone of brittle-plastic transition that lies between the two extreme brittle and plastic layers.While the dual mechanism model is so simple that overestimates the strength of rocks near the brittle-plastic transition zone.Although many studies about the deformation mechanism of brittle-plastic transition zone have been made,a＇flow law＇representation,which can describe the strength for the brittle-plastic transition,has not been formulated,and there has been little research about fluid effects;In addition,research on brittle-plastic transition usually focuses on temperature effects,while the research on the aspects of strain rate and fluid are relatively weak.Studies of deformation mechanisms of minerals in faults have indicated that brittle-plastic transition of some faults occurred in the same depth（temperature and pressure） and this phenomenon,which has been considered to be relevant to synseismic loading and postseismic creep in earthquake cycles and confirmed by distribution of focal depth,is due to the strain rate.The presence of high-pressure fluid in active fault at depth is proved by analysis of characteristics of fault fluids,and these fluids,which can evolve in pressure pertaining to fracturing and sealing processes,play a key role during the seismic cycle.The formation of high-pressure fluid（cracks sealing） has several mechanisms,but researches show pressure solution deposition is one of the main mechanisms which controls crack sealing kinetics