兰州观象台存放台阵在汶川特大地震中获取了10组三分量数字强震动加速度记录.本文依据这些实际观测资料研究了黄土场地在地震发生后的自由场地面运动加速度过程及其特征.结果表明在震源、场地和震中距相同情况下,场地上不同测点记录的加速度峰值存在一定程度的差异,较明显地反映了场地地形对EW分向地面自由场加速度的影响.10个测点的峰值加速度(PGA)均显示EW向大于NS向,而垂直向最小;各测点的傅里叶谱值,尤其是在小于1 Hz频段范围内,差异极小.%Paking array in Lanzhou Earth Observatary obtained ten groups of 3-directions strong ground motion records from the main shock of great Wenchuan earthquake. Based on the records the acceleration time history and characteristics of ground motion in loess site are studied. The result shows that peak ground acceleration (PGA) at different point in a small area of same site, with same seismic source and epicentral distance, had a certain degree of difference which obviously effected by site topography. In all ten strong motion observation points, PGA in EW direction were largest and PGA in the vertical direction were smallest. The difference of Fourier spectra in different points, especially for frequencies less than 1 Hz, is insignificant.
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