Stress Triggering And Fault Properties In The Rupture Process Of Large Earthquakes

The elastic rebound theory is the theoretical basis of earthquake occurrence,while the dislocation theory is the theoretical basis of numerical simulation of surface deformation and inversion of earthquake source,and the inversion of earthquake rupture processes is first based on these two theories.Earthquakes usually occur on faults in the elastic layers of the lithosphere,when a fault is deformed for a long time by the tectonic movement of a plate or active block,the elastic strain energy generated is accumulated continuously.Once the accumulated energy exceeds the limit it can bear,the fault will rupture and slide.After the rupture is over,the fault on both sides jumps back to the position of force equilibrium,and the elastic strain energy accumulated on the fault is released.In fact,elastic strain energy can be released in many forms:overcoming the friction of the fault surface into frictional heat energy;causing fault rupture or dislocation and permanent deformation of the crust near the fault;ground vibration in the form of seismic waves propagating in all directions.Therefore,fault rupture or fault friction,seismic deformation and seismic wave provide a good idea for us to study the mechanism of earthquake development.The rupture of compressed rock approximately follows the Coulomb failure criterion.According to Coulomb criterion,the earthquake will cause stress readjustment in the epicenter and its surrounding area.This change in stress field has implications for other faults as well.That is,an increase in Coulomb failure stress is likely to promote the rupture of the associated fault,while its decrease may delay or inhibit the rupture of the fault.Based on the inversion results of coseismic dislocation on the faults in the study area,the interaction between faults can be analyzed qualitatively;Considering the coseismic Coulomb failure stress changes,the triggering effect of the former ruptured fault on the subsequent ruptured faults can be analyzed quantitatively.Taking the 2016 Kaikoura MW 7.8 earthquake in New Zealand as an example,qualitative and quantitative studies were combined to further analyze the relationship between seismic faults.The rock experiments show that the fault movement can be described by a state-rate dependent friction constitutive law,and the critical slip distance DC and the velocity-dependent combination parameter for steady-state friction(a-b)are the main parameters of the physical properties of fault friction.It has been concerned by many people to discuss the parameter(a-b)to analyze the physical properties of faults.Therefore,this paper analyzes the critical slip distance DC.Theoretically,it is more scientific to determine the DC by stress change.Considering that the DC obtained in the laboratory cannot meet the requirements,this paper tries to take the 2011 MW 9.0earthquake in Japan as an example to estimate DC based on the seismic coseismic dislocation and rupture process obtained by inversion,and then describe the physical property of the fault according to the state-rate dependent friction constitutive law.Two typical earthquakes: the 2016 Kaikoura MW 7.8 earthquake in New Zealand and the 2011 MW 9.0 earthquake in Japan.The complexity of the 2016 Kaikoura MW7.8 earthquake in New Zealand is mainly manifested in the fault geometric characteristics,with up to a dozen of seismic faults,and this earthquake produce significant surface deformation,including scattered uplift and complex surface rupture.This paper analyzes the triggering relationship between each ruptured fault in the process of coseismic rupture by inverting the coseismic dislocations of 12 faults and calculating the Coulomb stress changes caused by them;The uniqueness of the 2011 MW 9.0 earthquake in Japan is mainly due to the difference in physical properties of the faults.The two deep and shallow dislocation concentrations indicate the existence of deep and shallow different asperities,and they control the fault movement in the Japan Trench region.Numerous historical earthquakes can be explained by asperities rupture.The study of two typical earthquakes shows that the geometric and physical properties of seismic faults are important directions to study the seismic fault hazard.