Research On Stochastic Simulation Method Of High Frequency Ground Motion Based On Improved Stochastic Finite Fault Method

China has a vast territory and frequent earthquakes,which are characterized by high frequency,high intensity,wide distribution and severe disaster.Research on earthquake engineering has always been a hot field.Due to the uneven distribution of seismic network and the lack of ground motion observation records in most areas,the seismic waves needed for structural seismic analysis are mainly obtained by artificial simulation.Most structures in practical engineering have small natural vibration period,and high frequency ground motion has a greater impact on such structures.In this paper,the random simulation method with better simulation effect of high frequency ground motion is selected.Firstly,the development history and research status of this method are summarized and summarized,its basic principle is introduced,and the advantages and existing problems of this method are described in detail.On this basis,more in-depth research is conducted.The main research work and achievements of this paper are as follows:(1)The basic principle and development history of random ground motion simulation method are introduced,the advantages and disadvantages of random point source method and random finite fault method and their application scope are summarized,the values and meanings of required parameters are explained in detail,and the existing problems of this method are discussed.(2)A simple derivation of the corner frequency expression is given according to the model and hypothesis used,and the irrationality of the corner frequency formula in the stochastic finite fault program is pointed out and some improvements are made.In order to solve the problem that the original stochastic finite fault program can only calculate the two dimensional S-wave,the basic principle of stochastic finite fault method for 3d ground motion simulation is presented and the program is modified.The simulated value of 3d ground motion time history obtained is compared with the observed value,and the better result is obtained.(3)By studying the finite fault model,a three-dimensional random finite fault method is proposed to calculate the underground field points,and the threedimensional ground motion time history is simulated by using this method.The seismic response of near-field earthquakes under strike-slip faults in threedimensional sedimentary basins is studied by combining the modified stochastic finite fault method and finite element method.(4)For the lack of strong ground motion records can consider to parameter uncertainty in ground motion simulation,aiming at the existing parameter uncertainty analysis method can both efficiency and precision of the question,introducing the multiplier method of dimension reduction to contain the uncertain parameters of ground motion acceleration mean value and variance,and compared with the monte carlo simulation method for validation.The results show that it is feasible to combine the dimension reduction method with the stochastic finite fault method to solve the random ground motion with parameter uncertainty.(5)The peak accelerations of 192 field points in 8 directions under 5 seismic magnituresare simulated and plotted by using the dimension reduction method of multiplier,and the results are consistent with the motion law of near-fault ground motions.(6)Considering the uncertainty of the parameters,the seismic response of sedimentary basin is analyzed,which is the same as the basin effect of the random finite fault method.