Study On Site Amplification Factor Of Bedrock Ground Motion Inversion Based On Surface Strong Motion Records

Many earthquake damage investigations can show that the site conditions have a great influence on the severity of earthquake damage.The different site conditions have different effects on the amplification or reduction of different frequency components of seismic waves,which makes the earthquake damage in the strong earthquake area much more destructive.Therefore,it is very important to study the effect of site conditions on ground motion peak.The site coefficient is an important parameter used to consider the influence of site in seismic design of structures,which is clearly stated in GB 50011-2010 and GB18306-2015.It is one of the main methods to study the site coefficient by using the measured acceleration records of the station array.Because the acceleration records at the underground bedrock contain input seismic waves and reflected seismic waves,it is obvious that the acceleration records cannot be directly used as input seismic waves,and the results obtained have large errors.Based on the actual surface ground motion records and real array field model is set up,by numerical method the model of onedimensional soil layer seismic inversion,which is based on a true surface inversion of strong earthquake records for bedrock acceleration input,finally calculates the surface and the inversion of the bedrock peak acceleration amplification factor and influence coefficient.The main research results and contents are as follows:(1)Total of 262 surface acceleration records were selected from 73 stations in the Ki K-net strong-motion seismograph network.In order to ensure the rationality of the calculation results,the selection conditions of ground motion wave meet the following three requirements: focal depth no more than 50 km,peak acceleration of the surface no less than 0.018 g,magnitude no less than 5,and epicenter distance no more than 100 km.According to the classification criteria of peak acceleration and site classification principle,28 groups were divided,each group contained 3 or more samples(a few only2 samples were collected).(2)Based on the borehole data of 73 stations,the inductive components of soil medium were calculated,and the corresponding soil dynamic parameters were selected.Total of 73 one-dimensional soil layer models were established.(3)The equivalent linearized seismic response of one-dimensional soil layer was analyzed by using SHAKE91 software,and the input acceleration of bedrock was obtained by inversion.The amplification factor of EPA based on the effective peak acceleration was calculated,and then the site coefficient of the effective peak acceleration of various sites was obtained.At the same time,the site coefficient based on the PGA of the peak acceleration of various sites is also calculated,and the results are similar.The final result is that: the magnification factor and adjustment coefficient of the ? type site are the largest,followed by type ? and type ?,and the type of the site is the smallest.This result is similar to some existing research results.Therefore,the estimation of site adjustment coefficient based on bedrock seismic wave inversion proposed in this paper can be used as a supplement to the existing methods.Finally,the future research work is prospected.