Classification Of The Daying River Site Category Based On The H/V Spectral Ratio Method

China is at the peak of the fifth seismic activity in this century,in terms of urban seismic disaster prevention and mitigation,in terms of urban seismic disaster prevention and mitigation,it is of great significance to determine the regional site category of each city to reduce seismic hazards and plan seismic mitigation,in which the remarkable cycles of different sites in cities and the amplification of bedrock ground shaking have a close relationship with the distribution of urban seismic hazards,so it is an important element of regional site category classification Therefore,it is an important element of regional site classification.Therefore,it is important to find a convenient,economical and reliable method to determine the site category in different areas of the city to reduce seismic hazards.Yingjiang County is located in the southwest of Yunnan Dehong Autonomous Prefecture,the edge of the Longling-Tengchong seismic zone,seismic intensity of 7degrees.Since ancient times,the earth’s crust has been frequently active and various earthquakes have been occurring.In this paper,a large number of ground pulsation tests were conducted on the Great Yingjiang site,and the final study led to the following conclusions:(1)To investigate the effects of different data processing methods,the results under different window functions,different bandwidth settings,inverse STA/LTA algorithms,and different horizontal component averaging methods were analyzed.The data measured by cd3 were smoothed by applying Parzen window,Cosine window,Rectangular window and Bartlett window,and it was found that the smoothing curves were basically the same after applying the first three window functions,and the smoothing curves were slightly different after applying Bartlett window,and the four window functions yielded basically the same remarkable frequencies.Five different bandwidths of Parzen windows were selected for comparison and analysis.The Parzen window with a bandwidth of 1.0Hz is used as the reference basis,and the ratio of standard deviation at 0.5Hz and 0.7Hz is more desirable.In general,when the bandwidth is taken as 0.5Hz,the Parzen window can meet the requirement of spectrum curve smoothing well.(2)The inverse STA/LTA algorithm was applied to 60 ground pulsation test data at the Daying Jiang site,and the analysis showed that the more the number of extracted time windows yielded the more stable the excellence frequency and the more reliable the results.The results calculated by comparing different parameter values were compared to determine the appropriate parameter values for the inverse STA/LTA method.Taking cd40 as an example,the root-mean-square method,geometric mean method,and average method were used to calculate the site H/V spectral ratio by the 3averaging methods.It was obtained that the three methods yielded exactly the same remarkable frequencies but different amplitudes,with the geometric mean method yielding the largest amplitude and the root-mean-square method yielding a slightly larger amplitude than the average method.The standard deviation at the excellence period is given for different sites by considering multiple measurement points.In order to minimize the dispersion of the data,the geometric mean method is used to calculate the horizontal components.(3)Compare and analyze the spectrograms of different sites,and analyze the difference of ground pulsation spectral characteristics in two sites with different degrees of softness and hardness,and conclude that the equivalent shear wave velocity of the site is large,the site soil is harder,the ground pulsation spectrograms have relatively more obvious peaks and wider frequency bands,and the amplification factor changes from 1.86-2.37 to 1.62-3.48.When the soil layer contains more soft and weak interlayer,the spectrograms show multiple peaks and the peaks are not The amplification coefficient is larger.(4)The H/V spectral ratio calculation was carried out,and the reliability of the obtained spectrograms was checked.With reference to the method of site category classification in the specification,the excellence frequency of each site was used to fit the curve with the thickness of the overburden and the equivalent shear wave velocity to determine the excellence period limit of class II and class III sites as 0.68 s.Using the box method and the formula method,the excellence period limits of class I～IV sites were determined by combining the three methods as follows: T≤0.09 s,0.09s<T≤ 0.64 s,0.64<T ≤ For the sites with the period of excellence near the boundary values of the II and III sites(0.544s～0.736s),the magnitude of the difference between the spectral curve and the standard curve shape was calculated to find out the site category.The site classification methods of period of excellence and spectral ratio curve correction were used respectively,and the correctness of the two methods was compared and analyzed.After the correction of spectral ratio curve,the correct rate of classification of Class II sites was increased from 65% to 75%,and that of Class III sites was increased from 40% to 60%.Finally,a method was established to classify sites in large areas based on a small amount of geological survey data and numerous ground pulsation test data.The 222 sites tested were classified by ground pulsation data,and the site category classification map of Dayingjiang was drawn to provide reference for the design of engineering design and seismic microzonation of Dayingjiang sites.