A set of dynamic centrifuge experiments were performed to assess the effect of the depth of the groundwater table on the seismic site response of silty sand. Silty sand was prepared in a laminar container. The testing program consists of experiments on dry as well as saturated soils and a test, which the groundwater table was below the soil surface. The specimens were spun in a centrifuge, then they were excited with a suite of seismic motions. Results show that 1) while the for peak ground acceleration amplification factor of the saturated soil was smaller than those for the dry soil, the Arias intensity amplification factor of the saturated soil was larger than those for dry soil. 2) as the depth of the groundwater table increased, peak ground amplification factor and short-period amplification factors increased, the mid-period amplification factors decreased. 3) the depth of the groundwater table influences the frequency content of the free field motion. 4) the unsaturated soil behaved stiffer than dry and saturated soils.
