2019 Volume 7 Issue 1 Pages 72-84
With the earthquake records obtained during the last 23 years, analyses of transfer function, cross-spectrum and coherence function have been performed for a rockfill dam named Aratozawa dam (74.4m high and with central clay core). Based on analysis results, the fundamental frequencies and acceleration amplification factors of the dam were investigated. It was found that the fundamental (first natural) frequencies and the acceleration amplification factors of the dam sharply decreased temporarily, after being struck by the Iwate-Miyagi Nairiku Earthquake on June 14, 2008. However, these characteristics recovered almost to their original status about a week after the main shock. By investigating the propagating behavior of seismic motion in the dam-foundation system, it has been pointed out that in the low frequency range up to the fundamental frequency of the dam, the response of the dam crest mainly depends on the seismic motion of the subjacent bedrock. On the other hand, in the higher frequency ranges, the contribution of the seismic motion of both banks may become dominant depending on frequency.
