高温高压条件下辉长岩的摩擦强度及其速率依赖性  

FRICTIONAL STRENGTH AND RATE DEPENDENCE OF GABBRO GOUGE UNDER ELEVATED TEMPERATURE AND PRESSURE

作　　者：何昌荣[1] 陶青峰[1] 王泽利[1] 

机构地区：[1]中国地震局地质研究所

出　　处：《地震地质》2004年第3期450-460,共11页Seismology and Geology

基　　金：国家自然科学基金 (4 0 2 74 0 2 4 );国家重点基础研究发展规划项目 (G1 9980 4 0 70 4 )共同资助

摘　　要：在干燥条件下对辉长岩的摩擦本构参数进行了实验研究。结果表明 :1 )辉长岩模拟断层泥的摩擦速度依赖性参数 (a -b)基本为正或者接近于没有速度依赖性 ,表明在干燥条件下不具备不稳定滑动的成核条件 ,对下地壳地震成核的可能性有参考意义 ;2 )摩擦强度在干燥条件下与Byerlee定律高度一致 ,表明在下地壳的高温环境下Byerlee定律仍可给出适当的强度估计 ,至少在干燥条件下如此 ;3)Byerlee定律给出的剪应力强度与正应力的关系中有一个截距 ,但是本研究中关于模拟断层泥的结果却没有明显的截距 。As most earthquake focal depths are concentrated in the upper crust (e.g. Chen et al ., 1983), previous studies on rate dependence of frictional strength have focused on granite that is typical in the upper crust (Lockner et al ., 1986; Blanpied et al ., 1995). However, recent reassessment of focal depth of many earthquakes revealed that some of them have been generated in the continental lower crust (Maggi et al ., 2000). Moreover, teleseismic imaging of the structure across the San Andreas Fault also suggested the existence of deep fault that cuts through the crust (Zhu, 2000). With this background, we need to pay more attention to intermediate and mafic rocks in the lower crust. Frictional resistance and the related rate dependence of such rocks are critical to understand the mechanical behavior of deep faults that cut the lower crust. Specifically, this is crucial for answering two important questions, namely: 1) Is it likely for earthquake to nucleate in the continental lower crust? 2) How much stress can the lower crust support? We conducted experiments on frictional sliding of oven dried gabbro gouge at elevated temperatures with a triaxial testing system using gas as the pressure medium. A gabbro gouge layer of 1 mm thick (particle size of the gouge<76μm) was placed along an inclined saw cut (35° to the loading axis) in a 20 mm diameter cylinder sample to simulate a fault with gouge. Two series of experiments have been conducted with normal stresses of 200MPa and 300MPa, respectively, with temperatures up to 616℃. For both normal stresses, the rate dependence of friction is either positive or approaching to neutral rate dependence. With normal stress of 300MPa, the values of steady state rate dependence are positive in most of the temperature range but show a minimum around 315℃ (approaching to zero). Variation of rate dependence under normal stress of 200MPa is less pronounced. Based on theoretical analysis on slip nucleation (e.g. Dieterich, 1992) and these experimen

关 键 词：辉长岩 摩擦强度 速率依赖性 地壳 

分 类 号：P588.124[天文地球—岩石学]