压扭性断层地震过程的Cusp型突变分析

将地震过程视为一力学系统的失稳现象,对压扭性断层地震提出了一个力学模型,导出了由线弹性围岩和具有软化特性的断层带介质组成的力学系统的势能表达式,得到了CuSp型突变模型的标准形式。用突变理论分析阐明了系统本身的几何和力学特性是系统稳定性的决定因素,外部作用是基本条件,外力作用方向对断层的稳定性和地震时所释放能量的大小起着重要作用。     

深部闭锁断层周围的应力场、形变场

本文用三维有限单元法模拟计算了深部闭锁断层周围的应力场、形变场,分析了它们的时空变化特征。认为:活断层周围的水平应力在断层附近略有减小;由断层闭锁引起的应力增强区和相对减弱区在其两侧反对称分布,闭锁区周围较大范围内应力增强,比断层端部更能积累巨大的弹性应变能而孕育较强地震;地壳应力、形变的逆向变化可能与震源孕育过程的不同阶段相联系。     

STRESS AND DEFORMATION FIELDS ABOUT A LOCKED FAULT IN DEPTH

In this paper the stress and deformation fields about a locked fault in depth have been imitated using 3-dimensional finite element method and their time-space variation features have been analysed. The authors consider tentatively that the horizontal stresses about an active fault decrease slightly near the fault. The distributions of stress increasing and decreasing regions due to the locking of a fault are skew-symmetrical about the fault. The stresses about the locked region are increased in a larger range, where great elastic strain energy is accumulated and a stronger earthquake is more easily developed than at the ends of the fault. Reverse variations of crustal stress and deformation may be related to the different stages of the seismogeny of an earthquake focus.