National Seismic Zoning Map Considering Site Effect

Local site conditions have become a hot issue in recent years,which can affect the transmission of ground motion,amplify ground motion in most areas,and possibly reduce ground motion in local areas,and have a great impact on the distribution of earthquake disasters.Therefore,the influence of site conditions must be considered when selecting ground motion parameters for seismic design.The fifth generation zoning map of China is based on the calculation results of class I bedrock site,and the seismic hazard distribution map of class II site is obtained through unified site amplification coefficient adjustment,but the seismic hazard distribution map of actual site is not directly given.Therefore,this paper used the topographic slope method to interpolate the national 30m borehole shear wave velocity(V_S30)distribution map,and introduced the NGA-West2ground motion attenuation relationship in the CPSHA calculation process to calculate the national seismic risk distribution map considering the site amplification effect.Its main work is as follows:(1)The key technology of Open Quake software used in the Global Earthquake Model(GEM)to calculate seismic hazard is studied,and the influence of the key parameters in probabilistic seismic hazard analysis on the hazard results is analyzed.The results show that the accuracy of meshing has a certain influence on the stability of the calculation results for different attenuation relations,and the influence trend is basically the same.Seismicity parameters have great influence on the hazard results,and the influence trend is basically the same.The fracture surface parameters have great influence on the hazard results,but the influence trend is different.Based on the Open Quake platform,the characteristics of CPSHA in China,such as the classification of three-level potential sources,uneven spatial distribution of seismicity,and the attenuation relationship between long and short axes,were integrated.(2)Based on Open Quake software,the source parameters obtained from the three-level potential source division of the Five Dynasties Zoning Map of China were used to conduct CPSHA of bedrock sites nationwide by using the attenuation relation of Yu Yanxiang in 2013 and the attenuation relation of NGA-West2 in 2014.The seismic hazard distribution maps with exceedance probability of 63%,10%and 2%in 50 years are obtained respectively.Based on the CPSHA result calculated based on Yu Yanxiang attenuation relation,the exceedance probability of bedrok site is 10%,and the class II site adjustment coefficient is amplified.The PGA values of 34 cities in China are basically within the PGA interval given in the fifth generation zoning map,which verifies the reliability of the calculation process.The CPSHA result of bedrock site calculated by using attenuation relation of NGA-WEST2 is slightly larger than that calculated by Yu Yanxiang.(3)The national 30m borehole shear wave velocity(V_S30)distribution map was obtained by interpolation based on Open Quake software and terrain slope method,and the attenuation relation of NGA-West2 was used to calculate the national seismic hazard distribution map considering the site effect.Compared with the site adjustment coefficient of the fifth generation zoning map in China,it is found that the site amplification coefficient of the soft site in some areas has exceeded the range of the site adjustment coefficient of the current zoning map.Based on the calculation results in this paper,the amplification coefficients of the four types of engineering sites in China were respectively counted.Except for the I-type sites,the distribution of the amplification coefficients of the II,III and IV sites was slightly larger than the range of the site adjustment coefficients in the zoning map.The research results of this paper can provide a basis for further considering the site amplification effect for the 5th generation of China's ground motion parameter zoning map,and provide a reference for the compilation of the next generation of zoning map.