Effects of soil structure on abnormal intensity in Hanyuan old town

Hanyuan town,Sichuan, is200 kmaway from the epicenter of the 2008 Wenchuan great earthquake, yet high abnormal seismic intensity was observed there. In order to analyze the effects of soil structure on the abnormal intensity at Hanyuan old town, based on scientific investigation on seismic damage distribution there, five boreholes were drilled on the frontal landslide slope of theBeihouMountainand the data of soil layer structures were obtained. On the basis of field test and laboratory experiment, the dynamic parameters of soils in different layers in Hanyuan old town were deduced. By inverting the strong motion data recorded at Jiuxiang strong-motion station and associate site information of this station, the time-history of ground motion was derived, and was taken as input bedrock waves for ground seismic response analysis. With 1-D equivalent linearization wave motion method, which is widely used in ground response analysis, Hanyuan old town ground motion parameters were calculated. The calculation result was compared with the strong motion record corresponding to intensity Ⅵ during the Wenchuan earthquake. The analysis result shows that the soil structure of Hanyuan old town region amplified ground motion, hence leading to abnormal ground motion. This is one of the main reasons for abnormal intensity.