Numerical Simulation Of Stress Evolution On Fault Based On Contact Elements Model

China lies at the southeastern of Eurasia plate, and it suffers from still-activetectonic movements and frequent earthquakes due to the interaction between Pacificplate, India plate, Philippine plate and Eurasia plate. Especially, the strongearthquakes mostly occurred in intraplate strike-slip faults. According to thecharacteristics of intraplate earthquake, we simulate stress involution and seismicactivity on the strike-slip faults by using the method of contact elements, in this paper.Firstly, we find out the effects that the chosen of contact elements parameters and thegeometrical shape work on the occurrence of earthquake. And on this basis, we studythe evolution of coulomb stress along Xianshuihe and Anninghe-Xiaojiang strike-slipfault in a seismic activity period in the past, and a further analysis of the coulombstress distribution on future risk region evaluation was given at last, which might helpto understand the earthquake mechanism at strike-slip fault.First, this paper studied the impact on seismic activity of strike-slip fault zone bythe medium parameters and the boundary dynamic. These factors include the frictioncoefficient, static/dynamic friction ration, loading rate, confining pressure andmedium parameters and boundary dynamic action, etc. Among them, as the frictioncoefficient grows, the interval time between ruptures during the process of stablesliding would increase; the greater of the maximum frictional force, the more staticsplit and the greater change in coulomb; static/dynamic friction ratio affects ruptureby using the maximum frictional force; the more the dynamic friction ratio, the morestatic friction coefficient. When the confining pressure increased, the interval time ofrupture during stable sliding will become shorter; the bigger the maximum frictionalforce, the more the slipping and the bigger change in coulomb stress; the increased inthe loading rate, the decreased in the rupture interval time, maximum frictional force,slipping and the coulomb stress.On the other hand, in order to find out the relationship between the geometricalshape and the rupture of the fault, we find this: because of the control of displacementin the inclined and bend model, stress changes during the process of block slipping, which will cause stick slip interval time changed; when the loading direction is thecontrary to the inclination of faults, the greater the tilt angle, the longer the slidinginterval time, and the accumulating and the releasing of the stress become moreintense. Instead, when the loading direction is the same with the inclination, theresults will come out totally opposed; the changes of coulomb stress act no differencebetween inclined and horizontal model; in the bend model, because of stressconcentrating, the rupture interval time of a larger slipping is shorter than thehorizontal model, and the concentration of stress is growing with the increasing of thedisplacement. Compared with the greater degree of bend model, the smaller degreemodel performs longer rupture interval time and smaller slipping. Although therupture interval time becomes shorter, the maximum of the shear stress almost thesame. The changes of coulomb stress mainly concerted on the bend area; slippingwork differently from different friction coefficients, but it concentrates at the convertpoint. The greater the fraction coefficient, the larger the slipping. The changes ofshear stress and coulomb stress happen in the larger friction coefficient area.Based on contact elements method, we do some analysis about Coulomb stress ofstrong earthquake on2-D strike-slip fault by taking Xianshuihe andAnninghe-Xiaojiang fault belt as examples. In the study of Xianshuihe, we calculatethe coulomb stress distribution of earthquakes with M≥6.7along the fault zone since1893, and we discuss the effects of coulomb stress changes caused by previous strongearthquake. Finally, we find that: the positive-affected zone concentrated at Zhuwo,Daofu-qianning, Qianning-Kangding, and the intersection of Xianshuihe andLongmenshan fault belt. We provide the same way on the analysis on theAnninghe-Xiaojiang fault, and finally we find that: coulomb stress distribution hereshow more complex because of the interaction of the east part and west part ofXiaojiang fault; the positive-effected zone concentrated on the north of Xiaojiangwest part and the south of Xiaojiang south part; on the other hand, almost the coulombstress of west part of Anninghe-Xiaojiang fault belt display negative-effected zone. Inthe end, it is worth noting that the Mabianxian (located at the east of Anninghe) showobvious positive-effected zone, which might induce earthquake.