| Determining the interfering factors and causes of periodic recurrence of large earthquakes is of great significance to the evaluation of the characteristic earthquakes of active faults.Based on the elastic rebound theory and the characteristic earthquake model,the paper uses a BPT model with a clear physical meaning to discuss the probability assessment of seismic hazards in the situation of interference events during seismic energy accumulation.This article defines the probability that the recurrence interval falls within 5% of the period is the periodic coefficient ?,and divides the periodicity of fault feature earthquake recurrence into 6 levels according to the periodic coefficient ?.According to the periodic coefficient index,when the perturbation volume is within 30%,active faults can be considered to have strong characteristics,and the periodic coefficient ? should not be less than 0.7.At this time,the disturbance coefficient ? should not exceed 0.21.According to the characteristics of fault seismic activity,the upper limit of its random disturbance coefficient can be determined.At the same time,it is found that the deterministic perturbations on different faults are not the same.According to the source of fault disturbances,the deterministic perturbations are divided into unloading disturbances and loading disturbances,which are expressed as delays and advances in the recurrence of characteristic earthquakes.Therefore,in this paper,if the BPT model is used to calculate the probability of a feature earthquake recurrence,it is necessary to first identify the deterministic disturbance on the active fault as much as possible and calculate the specific effect of the deterministic disturbance.Finally,reasonable parameters are selected considering the effects of random disturbances and all deterministic disturbances.In order to verify the accuracy of the aperiodicity obtained after the synthesis of all disturbances,and based on the 45 seismic sequences widely collected in the Chinese mainland,we first use the maximum likelihood estimation method to calculate aperiodicity of different sample sizes.And aperiodicity in the seismic sequence with different sample sizes is standardized,and then a universal aperiodicity(?_c = 0.37)is calculated.The correlation analysis results showed that aperiodicity was negatively correlated with the length and slip rate of the fault.Based on this,the application of the general aperiodicity(?_c = 0.37)was analyzed,and using the results of calculating the standard deviation of ?_c.we obtained that aperiodicity of the recurrence interval of strong earthquakes in the Chinese mainland is roughly in the range of 0.21 to 0.53.In order to calculate the influence of deterministic disturbances on the recurrence of large earthquakes ?t.We propose to calculate the impact time ?t respectively from the effect of strong earthquakes on the same and surrounding faults on the major earthquake recurrence by using seismic moment release rate method and Coulomb stress change.In this paper,we studied the change amount of major earthquake recurrence by taking four earthquakes with magnitude greater than 6.5 occurred at different fracture sections of the Xianshuhe fault zone as an example,they occurred on Daofu,Changcu,Zhuwo fault,respectively.The results indicate that the two strong earthquakes occurring along Xianshuihe Fault in 1904(M=7.0)and 1981(M=6.9)resulted in a delay of 80 years and 45 years of major earthquake recurrence on the Daofu-Qianning fault respectively,and the M7.3 earthquake in 1923 and the M6.8 earthquake in 1967 resulted in an advance of 35 years of major earthquake recurrence on the Ganzi-Luhuo Fault. |
PDF Full Text Request