Research On The Effect Of Basin Amplication Based On Observation Records

The amplication of ground motions by basins is a very important research content of seismic engineering.Its irregular shape and complex geological structure will cause strong amplication of ground motions by surface waves in the basin and cause serious damage to the surrounding structures of the basin.Observational data is an important method for analyzing basin amplication.This article studies the relationship between basin amplication and overburden thickness based on a large number of observation records.The main contents are as follows:1.Based on 480 seismic records in the Osaka Basin,using the traditional spectral ratio method,analyze the relationship between the amplication of the basin and the thickness of the overburden in each period.Studies have shown that the short-period(T=0.2s,0.5s)enlargement of the Osaka Basin is positively correlated with the overburden thickness(<1200m),and the long-period(T=3s)enlargement has a significant positive correlation with the overburden thickness(>1200m).Based on201 records in the Los Angeles Basin,Weihe Basin and Taipei Basin,the predicted value of the seismic acceleration response spectrum is obtained by using the rock attenuation relationship and the amplification factor under shallow conditions.Based on the residual difference between the predicted value and the actual observation value,the analysis of each The relationship between periodic basin enlargement and overburden thickness.Research shows that: for the Los Angeles Basin and Weihe Basin,short-period(T=0.2s,0.5s)enlargement has a weak correlation with overburden thickness,while long-period(T=2s,3s)enlargement There is a good positive correlation with the thickness of the cover layer.2.Based on the observation records of the Osaka Basin,Los Angeles Basin,and Weihe Basin,analyze the amplication of the basin from factors such as the magnitude,the position relationship between the epicenter and the basin,the focal distance,the angle of incidence of seismic waves,the components of ground motion parallel and perpendicular to the edge of the basin,etc.Correlation with cover layer thickness.The results show that:(1)Moment magnitude has little effect on the amplification of the Osaka Basin.(2)For the Los Angeles Basin and Weihe Basin,the correlation between the amplication of the basin and the thickness of the overburden layer caused by the earthquake below the basin is better than that of the earthquake outside the basin.For the Osaka Basin,this conclusion is only applicable to T=1s;the long period of the Osaka Basin(T= 3s)The amplication of the basin caused by the earthquake below the basin and the earthquake outside the basin has a significant positive correlation with the thickness of the overburden(>1200m).(3)Long period(T=2s,3s),earthquakes with a focal distance greater than 100 km cause a good correlation between the enlargement of the basin and the thickness of the overburden.3.The thickness of the basin overburden and the average underground shear wave velocity Vs-30 are the two most important factors that affect the amplication of the basin.Based on the observation records of the basin,the results show that the same overburden thickness(1000m-2000m),Japan The amplication of the Osaka Basin is higher than that of other basins.Based on the observation records of the Osaka Basin,comparing the traditional spectrum ratio method and the H/V(HVSR)method,it is found that the amplication obtained by the H/V method has a weak correlation with the thickness of the overburden,while the amplication obtained by the traditional spectrum ratio method has a weak correlation with the thickness of the overburden.Good correlation.Based on the observation records of the Los Angeles Basin,the Abrahamson ground motion model and the ASK14 model are used to calculate the predicted value of the acceleration response spectrum.Based on the residual difference between the predicted value of each model and the actual observation value,the research finds: the predicted value and the observed value of the ASK14 model The residual error of is weakly correlated with the thickness of the overburden.The residual error between the predicted and observed values of the Abrahamson ground motion model has a good correlation with the thickness of the overburden.