Numerical Simulation On The Echelon Faults Stick-slip Movement Process And Influence Factors

The echelon fault is one of the most common fault combinations,and the stick-slip movement of the fault is a mechanism of earthquake occurrence.The numerical simulation method can help us capture this phenomenon which is difficult to observe in the field.The two-dimensional echelon fault model is established in this paper,the contact element is established by using the mechanical parameters of viscoelasticity,the stick-slip movement process of echelon faults(earthquake related activities)and its influencing factors in the past 100000 years are simulated.By comparing the models with different parameters,it is found that:(1)Under boundary extrusion conditions,the echelon fault exhibits a stick-slip motion,the sudden dislocation of a fault is accompanied by stress drop.The maximum dislocation of the fault is 7.2 m,and the average recurrence period of earthquakes is 4846,which is comparable with the actual earthquake cases.(2)The spatial distribution of fault dislocation is uneven.Double influence of extrusion rate and overlapping area of echelon fault,the closer to the fault overlap area,the closer to the extrusion boundary,the more intense the stick-slip motion,the stronger the seismic activity,the greater the fault dislocation during the earthquake;on the contrary,away from the overlapping area,close to the end of the fault,the farther away from the extrusion boundary,the weaker the seismic activity and the smaller the amount of faults in the fault.(3)In the same geological conditions,the smaller the coefficient of friction,had higher frequency of the earthquake,the earthquake motion cycle is short,but the amount of dislocation is relatively small,easy of a smaller magnitude earthquake;The higher the friction coefficient,the lower the frequency of earthquakes,the longer the period of earthquakes,but relatively large amount of dislocation,prone to earthquakes of higher magnitude.(4)Under the same geological conditions,the greater the boundary displacement,the higher the frequency of earthquakes,the shorter the seismic movement period and the larger the dislocation.When the boundary displacement is smaller,the frequency of earthquakes will be lower,the longer the movement period of earthquakes will be,and the amount of dislocation will be relatively small,and earthquakes with lower magnitude are likely to occur.(5)When the friction coefficient and the boundary extrusion rate are constant,and the geometric spacing increases gradually from 10 km to 20 km,the stick-slip motion of the fault gradually weakens because the gap between the faults is too large,the interaction between the faults is reduced,and the tectonic stress field becomes smaller.