数值模拟静态应力扰动下的断层失稳:结果分析兼与Dieterich模型和Coulomb模型的对比  

Numerical simulation of fault instability due to an arbitrary static stress perturbation:A comparison with the Dieterich model and Coulomb failure model

作　　者：解孟雨 史保平[1] 

机构地区：[1]中国科学院大学,北京100049

出　　处：《地球物理学报》2016年第2期593-605,共13页Chinese Journal of Geophysics

基　　金：国家基金委(41574040);科技部<中国-东南亚毗邻区大震活动地球动力学研究>(2015DFA21260);中国科学院创新团队项目(KZZD-EW-TZ-19)共同资助

摘　　要：基于大量岩石力学实验,Dieterich和其他研究者(Dieterich,1978;Ruina,1983)首先提出了描述岩石摩擦过程的速率-状态摩擦定律(R-S摩擦定律).如今R-S摩擦定律已成为研究地震成核等地震演化机制的有效手段.Dieterich(1992,1994)最早提出了描述受静态剪应力扰动后断层失稳时间提前或推后的余震触发机制的解析模型.现在Dieterich模型已经成为解释余震随时间衰减规律的Omori定律等地震观测现象的有力工具.与之相对应,广泛使用的Coulomb应力失稳模型也可以给出断层受到静态剪应力扰动后,断层失稳时间的提前和推后量.Dieterich模型和Coulomb应力失稳模型基于不同的物理方法,所以在进行地震危险性评估时,二者均有各自的局限性.本文利用R-S摩擦定律控制的1-D弹簧-滑块模型,模拟计算了理论地震循环以及在不同静态剪切应力扰动下,失稳时间的提前和推后量的变化情况,然后将计算得到的时间提前和推后量分别与Dieterich模型和Coulomb模型的相应计算结果进行了定量化对比和差异性分析,并给出了相应的解释.数值模拟结果显示,对于R-S摩擦定律在参数不变的条件下,断层模型失稳时间的提前和推后量的大小强烈依赖于静态剪应力扰动的大小和作用时间,而且绝对值相同的正、负向静态剪应力扰动造成的失稳时间的提前和推后量的变化情况并不完全一致.在震后松弛/滑移阶段和闭锁阶段,时间提前和推后量是常数,且随静态剪应力扰动绝对值的增大而增大,两者的比值接近于1.0,这与Dieterich模型和Coulomb模型的结果是一致的,相应的差值小于两模型结果的10%.而在自加速阶段,模拟计算结果则存在与Dieterich模型和Coulomb模型结果不同的特征.首先,在自加速阶段模拟计算结果均偏离Coulomb模型,而且时间提前和推后量的比值小于1.0,相异于Coulomb模型的论断.不过当受到正向静态剪应力扰动后,DBased on the laboratory′s experiment related to the rock friction,Dieterich and other researchers（Dieterich,1978;Ruina,1983）first introduce rate-and-state friction law（R-S Friction Law）.Currently,R-S law has emerged as an effective tool for the study of earthquake faulting,such as earthquake nucleation.Later,Dieterich（1992,1994）first proposed an earthquake triggering model used to describe the time advance or time delay of an earthquake due to the static shear stress change.The Dieterich model has become a powerful tool in explaining many seismic observations,including the Omori law related to the aftershock decays with time.In other hand,the widely-used Coulomb failure model can also be used to estimate the time advance and time delay of an earthquake after applying a static shear stress change.Due to the different physical approaches between the Dieterich model and the Coulomb failure model,there exists a certain limitation for both models used in the seismic hazard analysis.In this study,we try to find out what decides the time advance or time delay of an earthquake due to the static shear stress change,the difference of variation of the time advance or time delay and figure out the limitations for Dieterich model and the Coulomb failure model.We first use the 1-D spring-slide block model governed by the R-S law to simulate earthquake cycle and triggered seismic activities caused by different static shear stress changes.Then we compare the simulation results separately with the solutions given by the Dieterich model and the Coulomb failure model,and the differences between our numerical simulation and the Dieterich and Coulomb models are discussed.Our results indicate that,at postseismic/afterslip stage and interseismic stage,the advanced or delayed time is constant and increases with the absolute values of static stress load growing.Moreover,the ratio of the advanced and delayed time is about 1.0.These phenomena could be predicted by both Dieterich′s model and Coulomb failure model,and the dif

关 键 词：速率-状态摩擦定律 静态剪应力扰动 Coulomb应力失稳模型 Dieterich模型 失稳时间提前量 失稳时间推后量 

分 类 号：P541[天文地球—构造地质学]