Comparison Of Horizontal And Vertical Ground Motion Coherence Functions

The spatial variation of ground motion is often described by the spatial correlation of ground motion.The quantitative method is used to express the spatial correlation of ground motion,which is often expressed by coherence function.Up to now,people mainly use ground motion coherence function to describe horizontal ground motion,and few people study vertical ground motion,let alone compare the similarities and differences of horizontal and vertical ground motion coherence functions.Therefore,this paper focuses on the horizontal and vertical ground motion coherence functions,and compares the relationship between the two and the laws under the magnitude and impact factors.The main research contents are as follows:1.Five representative seismic records of Taiwan SMART-1 array were selected,and a series of treatments were used to obtain the calculated data.The horizontal direction(NS)and vertical(V)acceleration records of each seismic record were selected to calculate the central station C00.Coherence function values with the inner ring,the middle ring and the outer ring station,and then the calculated coherence function values are fitted.The coherence function models used in the fitting are: Abrahamson coherent function model and LOH coherent function model,fitting tool Use 1stOpt.2.The variation of horizontal coherence function and vertical coherence function with frequency and station distance is compared.As the frequency and station distance increase,both horizontal and vertical coherence functions show a decreasing trend.However,at short-range low frequencies,the horizontal and vertical coherence functions are different.As the frequency increases,the difference between the horizontal and vertical coherence function curves decreases and tends to be consistent.3.Factors such as magnitude and source distance have an effect on the horizontal and vertical coherence functions.The magnitude has a significant influence on the vertical coherence function.When the distance is short,the larger the magnitude is,the larger the coherence function is,and the longer the distance is.The smaller the source distance,the easier the horizontal and vertical coherence functions tend to be.