Seismic record analysis of the Liyutan earth dam

In this paper the authors present an analysis of the seismic records of the Liyutan dam, which is a zoned compacted earth dam. It is 96 m in height, and it suffered some minor cracks and settlement during the 1999 Chi-Chi earthquake. A large amount of seismic motion has been recorded for 42 past earthquake events. These records were used to analyze the vibration characteristics of the dam. The fundamental frequency and nonlinear amplification of the peak ground motion of the dam body have been clearly identified. Based on the fundamental frequency identified from the small earthquake data, the seismic motion of the dam during the Chi-Chi earthquake could be well simulated by an equivalent linear dynamic procedure. An empirical decomposition method was used to decompose the Chi-Chi earthquake motion histories, from the top and the bottom of the dam, into several orthogonal and complete intrinsic mode functions (IMFs). These IMFs show that the low frequency parts of the seismic motion at the top and bottom of the dam are nearly the same, however, the high frequency parts are significantly amplified when the seismic motion propagates from the bottom to the top of the dam.