【摘要】 基于单自由度弹簧-滑块模型,滑移速率和状态相依赖的摩擦关系可用于对断层内部地震成核和断层失稳过程的定量化描述.Dieterich(1994)余震触发理论模型首次给出中强震后区域应力场受到静态应力扰动后所导致的区域地震活动性的时空变化特征,近期研究也表明Dieterich理论模型可进一步推广至依赖时间的地震预测模型的建立.本文从简单直观的断层群体化概念模型出发,推导出了包括静态剪应力和正应力扰动作用下广义Dieterich解.同Dieterich经典解相比,广义Coulomb应力变化:ΔCFFG=Δτ-(μ0-α)Δσ取代了Dieterich方程中原有的剪切应力扰动Δτ.从而表明余震发生率R同作用于断层上的正应力的变化(扰动)有着密切的相关性.进一步,我们讨论了传统Coulomb应力变化(扰动)模型在地震预测过程中可能存在的局限性.以1976年MS7.8唐山大地震的主余震序列为例,采用本文中得到的结果,并结合视时窗分段方法,拟合了该地区地震活动性的时间演化过程.结果表明,除Coulomb应力变化(扰动)的影响外,主震前后加载于断层上的剪应力速率变化可对早期余震发生率产生很大影响.更多还原

【Abstract】 Based on the spring-slide block model,earthquake nucleation related fault self-acceleration to failure could be intuitively and quantitatively described by the rate/state-dependent friction law.In the earthquake triggering model,Dieterich(1994) first proposed that the temporal and spatial evolutions of the seismicity vary with the static shear stress change or perturbation caused by moderate to large earthquakes,which has been used in the physics-based explanation of the Omori′s law.Recent studies also show that the Dieterich′s model can be further extended to time-dependent earthquake forecast modeling.From fault-population-modeling point of view,in this study we have derived a generalized Dieterich solution related to the aftershock triggering process in which the effects of the fault normal and shear stress changes have been involved in the current consideration.Compared with previous Dieterich′s solution,the Coulomb stress change of ΔCFFG=Δτ-(μ0-α)Δσ has been introduced in our solution instead of the only shear stress change of Δτ used in the Dieterich′s model.The results also imply that the normal stress change,Δσ,plays an important role relating to the aftershock seismicity.In addition,we discussed the possible limitations in the calculation of earthquake occurrence rate by using a simple Coulomb Stress Change Model without involving time-dependent non-linear phenomenon in the fault evolution.Using the solution obtained in this study,we fitted the time-dependent seismic variation around Tangshan region due to the 1976 MS7.8 Tangshan earthquake.The results indicated that,around the main fault,the shear stress rate change before and after the mainshock could exhibit a significant impact on the early aftershock rate change,as well as the Coulomb stress change.更多还原