Abstract: Site conditions have great influences on ground motion. It is important for ground motion correction to study its characteristics under different site conditions. Taking Jiuzhaigou earthquake as an example, 198 3-component seismic ground motion records at 66 stations and kilometer grid DEM (Digital Elevation Model) data from Shuttle Radar Topography Mission are collected, and site characteristics are analyzed from several aspects. Firstly, the site of Jiuzhaigou area is classified by using DEM data according to Wald’s gradient method. Then the characteristics of acceleration time history, acceleration response spectrum and ground motion attenuation are discussed under different site types. The results show that, in the absence of measured data, topographic slope can be used as an alternative index of Vs30, and the site can be classified quickly by slope method. The site characteristics of the stations can be analyzed from different aspects by using seismic ground motion records. Different site types exhibit different effects on the ground motion, and the soil layer shows obvious amplification effect on the ground motion. The results in this paper can provide a basis for the correction of ground motion.

Key words: DEM, Seismic ground motion records, PGA, Site classification, Site characteristics