Study Of The Nucleation Process On The Seismic Fault

Based on the rate-and state-dependent friction law,the influence of the relevant parameters of the constitutive law is simulated on the nucleation and slip process of the fault.First of all,we can obtain the influence of the fault size,the nucleation scale and other parameters on the nucleation cycle of the fault.Secondly,we use the Xianshuihe fault zone model to simulate the nucleation process by segmenting.At last,the impact of static stress and dynamic stress are simulated on the Xianshuihe fault by using the historical seismic statics.The static stress is loaded in the form of stress step and dynamic stress is applied in the form of pluses and wave packets.The results of the study are as follows:1.The nucleation cycle of the fault will be changed with the alter of the fault parameters except for ?.The value of a-b determine the occurrence of the stick-slip on the fault.The increase of the fault size,the decrease of the nucleation dimension,and the decrease of the characteristic displacement will reduce the average nucleation period.In addition,the increase of nucleation scale and the value of a-b will increase the slip of the fault.2.The study of static stress perturbation on the fault shows that just the magnitude of the Coulomb stress has the influence on nucleation cycle.The stick-slip will be advanced if the value of the stress is positive,the stick-slip will be delayed if the value of the stress is negative.The change of the fault nucleation time will be increased if the stress perturbation value increases.However,the positive stress perturbation has a stable value for the nucleation advanced time of the fault and the negative stress perturbation does not converge to the delay time of fault nucleation instability.3.According to the study of the dynamic stress perturbations in the form of pulse we get that the influence of the same shear stress and normal stress perturbation on the slip time of faults are similar.The larger the magnitude of the pulse,the greater the influence on the failure time on the fault.The positive stress effect has a convergencevalue and the negative stress has no convergence value on the nucleation failure time of the fault.The increase of pulse duration makes the slip advancement of the fault increase and finally tends to be stable in a certain time range.4.For wave packet disturbance,the advanced time of the fault failure caused by the normal stress is smaller than the shear stress.The advanced time caused by the normal stress has the phase lag compared with the advanced time curve caused by the shear stress.The change of fault failure time increases with the stress perturbation.The curve with smaller stress perturbation has phase lag compared to the curve with larger stress perturbation.Normal stress disturbance accelerates fault slip while negative stress has delay effect.The negative stress curve has a phase delay with respect to the normal stress curve.