Analysis And Research On Seismic Attenuation Relationship In Northern Shaanxi

At present,countries around the world have studied various aspects of seismic over-prediction,but so far no feasible methods have been studied for seismic over-prediction,and only seismic disaster prevention and mitigation work is carried out for seismic.For China's earthquake researchers and construction projects,only good site seismic safety evaluation work before construction to improve the ability of engineering construction sites to defend against seismic hazards.Engineering site seismic safety evaluation work is mainly to select the appropriate ground vibration attenuation relationship to determine the site ground vibration parameters for seismic protection of buildings(structures),to achieve the purpose of effective seismic disaster prevention and mitigation.Therefore,it is very important to analyze and study the ground vibration attenuation relationship of the site for the seismic protection of the project.Professor Yu Yanxiang divided China into four seismic regions:the eastern China seismic region,the medium-strong seismic region,the Xinjiang region,and the Qinghai-Tibet region.The ground shaking parameter attenuation relations are adopted from the western United States,and the attenuation relations are established on the basis of the site seismic frequency,magnitude size,and stratigraphic structure of earthquake propagation.It is more suitable for engineering sites in areas with high seismic frequency and abundant seismic data.For areas with low seismic frequency,lack of seismic data and complex stratigraphic structure,the seismic protection parameters will be greatly affected if the western U.S.ground-vibration attenuation relationship is adopted directly.Therefore,this thesis analyzes and studies the ground vibration attenuation relations in northern Shaanxi Province.First,based on the full collection of seismic data in northern Shaanxi and surrounding areas,the single random variable weighted least squares regression method and multiple robust regression method were used to regress the seismic data;meanwhile,on the basis of the elliptic long-short axis joint attenuation model,the attenuation relationship between seismic intensity of engineering sites was established.Based on the attenuation relationship between seismic intensity and ground shaking,five different mapping principles were used to map the attenuation relationship of ground motion in northern Shaanxi according to the western U.S.seismic attenuation relationship,and the corresponding ground motion attenuation data were obtained;then the mapped ground motion parameters were fitted by stepwise regression method,and the ground motion attenuation relationship in northern Shaanxi under five different mapping principles was finally obtained.Then,the mapping data were fitted with the stepwise regression method to obtain the ground shaking attenuation relationships in northern Shaanxi under five different mapping principles.The mapping transformation principle,i.e.,the midline mapping principle,is most suitable for northern Shaanxi,and the feasibility of this paper is verified by comparing and analyzing the ground shaking attenuation relations with those of the neighboring North China and Western China medium-strong seismic regions.Secondly,considering the influence of site conditions,the CB08 model established by Campbel and Bozorgnia in the NGA program is used to simplify and modify it,and the Vs30 values needed in this model can be used from the actual measured values of boreholes;for the areas lacking the actual measured Vs30 data,the value of Vs30 can be projected by the slope calculation method through the connection between Vs30 and slope.Establish the relationship of ground vibration attenuation with higher suitability of engineering site conditions in northern Shaanxi.And compare it with the medium-strong seismic zone,western region and the ground vibration attenuation relationship established by using the mapping conversion method to verify the feasibility of this attenuation relationship.Finally,based on the ground vibration attenuation relations established in this paper,the ground vibration peak acceleration attenuation relations of the engineering site in northern Shaanxi region are determined,and the response spectra of the site with 63%,10%and 2%exceedance probability in the next 50 years and 63%,10%and 2%exceedance probability in the next 100 years are derived.The seismic acceleration response spectra are also fitted in order to calculate the ground vibration parameters of the corresponding engineering site so that they meet the requirements of ground vibration parameters suitable for the seismic design of the site.