基性岩摩擦本构参数与下地壳地震成核的可能性  

FRICTION CONSTITUTIVE PARAMETERS OF MAFIC ROCK AND POSSIBILITY OF EARTHQUAKE NUCLEATION IN THE LOWER CRUST

作　　者：谭文彬[1] 何昌荣[1] 

机构地区：[1]中国地震局地质研究所,北京100029

出　　处：《地震地质》2007年第1期161-171,共11页Seismology and Geology

基　　金：国家自然科学基金(40574080);国家基础研究发展规划项目(2004CB418405)共同资助

摘　　要：摩擦滑动的力学行为能够很好地由速率和状态依赖性摩擦本构关系来描述。文中对地壳岩石滑动稳定性的控制因素进行了综述：1）微小扰动对摩擦滑动的影响分析（线性分析）表明，摩擦滑动中不稳定产生的重要条件是速率依赖性参数a-b〈0，在这种条件下，地震滑动可以在断层上成核；2）下地壳的水含量测定表明，可能存在“干”、“湿”两种情况，而已有岩石流变实验结果表明稳定大陆内部下地壳在干燥条件下为脆性变形行为；3）近年来发现一部分强震发生在基性的下地壳，使辉长岩高温高压摩擦实验受到重视。干燥条件下辉长岩的摩擦实验研究表明，在420—615℃的温度范围内，速度弱化可能是典型的滑动行为。综合考虑较冷大陆内部下地壳可能出现的“干燥”条件以及在此条件下不大可能发生塑性流动等相关因素，这一结果可能就是在一些地区下地壳发生地震的原因。Mechanical behaviors of frictional sliding can be described well by rate- and state- dependent friction laws. This paper reviews factors that control sliding stability of crustal rocks, and summarizes as follows： （1） analysis of small perturbation around steady state sliding （linear analysis） shows that an important condition for self-sustained instability to occur is a negative rate dependence of friction （a - b 〈 0） . Under such a condition, earthquake slips can nucleate on active faults. （2）Measurement of water content in crustal rocks implies that both ＂dry＂ and ＂wet＂ conditions＇in the lower crust are possible, and previous creep experiments show that deformation mechanisms under dry conditions are notionally brittle fracture and faulting. （3） Attention has been paid to gabbro under high pressure and temperature as a number of strong earthquakes were discovered to have occurred in the lower crust. Experiments on dry gabbro indicate that velocity weakening may be the typical sliding behavior with temperature ranging from 420℃ to 615℃. Synthetically considering the relevant conditions such as ＂dry＂ condition that may exist in relatively cool interior of continental lower crust, and mafic rock that is not likely to deform by plastic flow under such conditions, we may extrapolate this result to actual tectonic settings where the environments are more complex. This may explain why earthquakes occur in the lower crust in some areas.

关 键 词：摩擦 粘滑 高温高压 地震 孕震构造 下地壳 

分 类 号：P315.1[天文地球—地震学]