【摘要】 余震触发机制的Dieterich解析模型被广泛应用于区域地震活动性的定量分析以及依赖时间的概率地震预测模型的建立等方面.基于滑移速率和状态相依赖的摩擦定律和弹簧-滑块模型,从Dieterich断层滑移速率方程出发,给出了静态应力扰动下触发地震的时钟提前或推后的近似解,从而明确地阐明了触发地震的产生机制与断层的演化过程密切相关,并与传统位错模型下库仑应力扰动时间提前或推后量作了比较.采用对数线性拟合方法求得了汶川MW7.9主震后余震序列持续时间,符合Dieterich理论结果.以汶川余震序列为例,给出了两种不同的应力扰动模式在该余震序列中的应用.结果表明,经典Dieterich扰动解无法给出主震发生后即时余震数量的异常增加,而考虑主震前后剪应力速率变化的Dieterich分段解则可反映出余震发生率及个数随时间的演化特征.更多还原

【Abstract】 The analytic solution of earthquake triggering mechanism put forward by Dieterich has been widely used in quantitative analysis and description of regional seismic activities,and in the development of time-dependent earthquake prediction model.Based on the spring-slider model with a combination of rateand-state-dependent friction,starting from the fault slip rate evolution equation proposed by Dieterich,we have derived the equation called clock advance/delay related to the earthquake faulting instability under the Coulomb stress perturbation.In comparison with the simple dislocation model,the current result suggests that the generation of earthquakes is actually related to the state of fault evolution.For the 2008 Wenchuan MW7.9 earthquake sequence,we have estimated the possible time duration of aftershocks caused by main shock,both from theoretical inferring and empirical relation,and the result is similar to each other.Furthermore,two different stress change models have been used in the calculations of aftershock’s seismicity rate and cumulative number.These results suggest that the classic Dieterich stress change model could not fit the anomalous event increase well during a very short initial phase after the main shock,while the modified Dieterich model,which concerns the temporal variation of the fault shear stress rate,could be used to quantitatively describe the temporal evolution of aftershock decay.更多还原