Study On The Relationship Between Instrumental Seismic Intensity Increment And Site Amplification Factors Relative To Bedrock

Seismic intensity reflects the strength of the ground shaking caused by the earthquake,it was evaluated by artificial field investigation after the earthquake,and the magnitude of earthquake intensity is an intuitive reflection of the average earthquake damage in a certain region.Compared with the seismic intensity,the instrumental seismic intensity is calculated from the post-earthquake ground motion data,which removes the subjectivity of the manual evaluation of the seismic intensity,and the calculation is simple,fast and more objective.Chinese instrumental intensity increment(ΔI_china)is defined as the difference of instrumental intensity between soil layer and adjacent bedrock.A series of studies are carried out onΔI_chinaand the amplification factors of ground motion parameters（defined as the ratio of ground motion parameters between soil layer and adjacent bedrock）with data of KIK-net.The main achievements of the thesis are as follows:1.The variation law of ground motion parameter amplification factors with intensity of ground shaking.Based on more than 56,000 sets of data from 56 stations in KIK-net network,the variation of different ground motion parameters amplification factors（AF_X）with intensity of ground shaking is studied.The results show that:（1）Different ground motion parameters amplification factors increase first and then decrease with the increase of PGA,but the variation ranges of different parameters are different.（2）For the same ground motion parameter amplification factor,the value of Class II site is generally greater than that of Class I1 site,and the value of Class D site is generally greater than that of Class C and Class B sites,basically satisfying the same PGA conditions,the ground motion parameter amplification factor value gradually increases as the site becomes softer.2.The variation law of Chinese instrumental seismic intensity increment with intensity of ground shaking.Based on more than 56,000 sets of data from 56 arrays of KIK-net,the variation law of Chinese instrumental intensity with intensity of ground shaking is studied.The results show that:ΔI_china increases approximately linearly with PGA,and then decreases gradually when it reaches a certain threshold,and in the regression results,there is no significant difference in different directions.By comparing the mean regression curves ofΔI_china with PGA under different site types,it is found thatΔI_chinaincreases gradually with the site becoming softer under the same PGA.In addition,the increase range from class B to Class C is greater than that from class C Class D,and the curve of Class C and Class D is very close on the whole.In addition,comparing the nonlinear response thresholds of different site categories,it can be seen that the site category has no significant influence on the threshold of nonlinear site response.3.Relationship between Chinese instrumental seismic intensity increment with different ground motion parameters amplification factors.Based on 2182 sets of ground motion records of 10 earthquakes,ΔI_china and amplification factors of 18 ground motion parameters are calculated,and the empirical relations between them are established under different site types by nonlinear regression analysis method.The results show that:The regression results ofΔI_china and the amplification factors of 18 kinds of ground motion parameters are good overall,and there is an obvious positive correlation trend,the amplification factor(AF_a0.3),peak acceleration amplification factor(AF_PGA)andΔI_china are highly correlated.However,AF_{Avg Sa} and effective peak velocity amplification factor(AF_EPV)have low correlation withΔI_china.Due to different site classification methods,the regression correlation coefficient of Class B,C and D sites in the United States is higher than that of Class I1,II and III sites in China,and the data dispersion is smaller.4.Variation rules of Chinese instrumental seismic intensity increment with ground motion parameter amplification factors in the bedrock.According to the ground motion records of 28 KIK-net station arrays with V_S（30）exceeding 1000m/s,the variation law of the Chinese instrumental intensity increment and ground motion parameter amplification factors with the intensity of ground shaking on the bedrock site was studied.And the relationship between them were analyzed.Influence of epicentral distance on Chinese instrumental intensity increment and different ground motion parameter amplification factors were analyzed.