Research On The Amplification Effect Of Newmark Cumulative Displacement And The Arias Intensity Attenuation Relationship In Sichuan-Yunnan Region

Earthquake-induced landslide is a common secondary disaster of earthquake in high intensity mountainous areas.It has caused great casualties and economic losses in Western China.Seismic landslide risk zoning and targeted fortification are the most effective measures to reduce disaster losses.Newmark cumulative displacement is the main evaluation index of seismic landslide risk zoning.Nowadays,the calculation of Newmark cumulative displacement and empirical model are realized through the recordings of free site.Due to the topographic amplification of ground motion,the ground motion of slope body will be greater than that of ground motion station,which also leads to the low calculated value of cumulative displacement,thus underestimating the risk of seismic landslide.On the other hand,it is strong correlation that between the cumulative displacement and the ground motion parameters,especially the arias intensity,resulting in many empirical relationships between the cumulative displacement and the ground motion parameters.The research on the prediction relationship(GMPE)of arias is still in the blank stage in China.Therefore,this paper discusses the topographic amplification effect of Newmark cumulative displacement and the Arias intensity attenuation relationship in Sichuan Yunnan region.The main contents and phased achievements of the study are as follows:(1)According to the strong motion recording of Pingwu station of Wenchuan earthquake in 2008,it is found that the Newmark cumulative displacement has amplification effect,which is different from the real landslide example.It is more accurate to use the cumulative displacement obtained from the ground motion calculation on the slope to predict the seismic landslide risk.Different empirical models of cumulative displacement proposed by scholars from various countries since 1988 are summarized.It is verified that the empirical formula of cumulative displacement is also applicable to seismic waves at slope affected by amplification effect.(2)The dynamic simulation of slopes with different slope heights,slopes and parameters is carried out by Flac3d software.According to the dynamic response changes of Arias intensity and other parameters at different monitoring points on the upper part of the slope,the influence laws of different factors on the topographic amplification effect of the slope are obtained,which compared with PGA,the influence laws of different factors on the Newmark displacement are obtained.(3)Based on the strong motion data of Sichuan Province and Yunnan Province,the Arias intensity attenuation relationship in Sichuan Yunnan region is calculated,the residual analysis and fitting degree verification are carried out,and the Arias intensity model is compared with that of other scholars.In view of the effect of near fault effect of large earthquakes on the ground motion prediction equation(GMPE),the possible hanging wall effect and fracture directivity effect are analyzed.(4)Selecting Jiuzhaigou County as the main research area,the critical acceleration value of the area is calculated and obtained based on the geological conditions of Jiuzhaigou and the DEM data.Combined with the arias intensity distribution calculated according to the Arias intensity attenuation relationship,the cumulative displacement is calculated through Newmark empirical model.The cumulative displacement value is used to predict the landslide risk in the seismic area,and compared with the real landslide data.The results show that the Newmark cumulative displacement obtained from the seismic ground motion calculation of the slope is more accurate,which is consistent with the real earthquake landslide situation.In the subsequent seismic landslide risk zoning,attention should be paid to the impact caused by the topographic amplification effect.Combined with the specific law of the cumulative displacement amplification effect in this paper,a more reasonable cumulative displacement calculation formula can be proposed or the basis for the modification of the existing calculation methods can be provided.At the same time,the arias intensity attenuation relationship in this paper is widely used in Sichuan and Yunnan,which makes up for the blank of the arias intensity attenuation relationship in China.The Newmark cumulative displacement calculated according to the attenuation relationship is more accurate and has good accuracy in the prediction of seismic landslide risk.The above research work is of great significance to the risk analysis of earthquake induced landslides and the prevention and control of earthquake induced landslides in high intensity areas in Western China.