Multi-scheme Of Probabilistic Seismic Hazard Evaluation

Seismic hazard assessment is based on the study of the regional seismic activity,seismic structure background and so on.It's predicted or evaluated earthquakes and earthquake induced geological disaster in the future of the project site.At present,we adopt the probabilistic seismic hazard analysis method which is prevailing in the international society.It gives a certain year under different probability levels of ground motion parameters of the engineering site.Seismic region or belt and potential seismic source zone reflect the spatial inhomogeneous of seismicity.Seismic belt parameters reflect the temporal distribution characteristics of seismic activity.There are a series of uncertainties of probabilistic seismic hazard analysis in delineating seismic region and potential seismic source zone and in setting seismicity parameters and ground motion attenuation relation.However,the uncertainty directly affects the final determination of the ground motion parameter.So it is necessary to conduct a detailed study of the effect of uncertainty on the results to provide the basis for delineating potential seismic source zone and setting seismicity parameters in the seismic hazard assessment of the nuclear power plant.This paper takes the Guangxi nuclear power plant as an example.After analyzing region seismic activity and geological structure background,this paper discusses and analyses seismic belt,potential seismic source zone,associated seismicity parameters and other uncertainties in different probability of exceedance of bedrock peak acceleration impact on the site.At last,this paper analyses the sensitivity of the seismicity parameters and discusses the source of the uncertainty from the fracture activity and seismicity.The conclusions have been obtained as following:(1)On the basis of seismic activity in the site area,seismic structure characteristics and so on,this paper gives the boundary of the key potential seismic source zone,upper limit magnitude of potential seismic source zone.The probabilistic seismic hazard analysis shows,the upper limit magnitude of potential seismic source zone adjacent to high magnitude upper limit magnitude and potential seismic source zone and site distance have a great influence on the ground motion parameters.(2)Multi-scheme comparison study showed that the corresponding area in the low probability of exceedance peak acceleration parameters have much more influenced than the corresponding annual probability of exceedance high value peak acceleration in the change of parameters.The annual of exceed probability of low levels play an important role than the annual of exceed probability of high levels in the change of the focal depth.Parameter uncertainty is the root cause of the level of awareness of the fracture activity and seismicity.(3)Ground motion attenuation law may exert a greater influence on the ground motion of the site.By the comparison and analysis,the paper calculated by south China earthquake ground motion attenuation laws of peak acceleration higher than that of obtained by ground motion attenuation law of eastern China peak acceleration.From the source and the safety of the project,the ground motion attenuation law in south China is more suitable for this region.(4)The sensitivity of seismicity parameter analysis shows that when the value of b is constant,the bedrock level to peak acceleration increases with increasing v4.When v4 certain value,the bedrock level of the peak acceleration increases with b values decrease.The b-value is more sensitive than v4 in peak acceleration.