Characteristics of frequency content of near-fault ground motions during the Chi-Chi earthquake.

The frequency content of earthquake ground motion is very important because it affects the dynamic response of structural systems. In the paper, we use five scalar parameters (the response spectral predominant period T _p, smoothed spectral predominant period T _o, Fourier amplitude spectral mean period T _m, equivalent pulse period T _v, and the pseudo-velocity spectral predominant period T _pv) reflecting the characteristics of frequency content of strong ground motion to examine the near-fault three-component motions during the 1999 Chi-Chi earthquake. The result indicates that the frequency content of near-fault motions at the Hanging wall is less than that at the foot wall; T _p shows a smaller value than that of T _o and T _m and it emerges a reverse relation of three-component motions as compared with that of T _o and T _m; T _v and T _pv of the near-fault motions at the north end of the rupture display a similar trend to that generated by the rupture directivity effect of strike-slip faulting. We therefore conclude that these observations are useful in the formulation of near-fault design spectra for seismic codes and in zoning studies in seismic risk. [ABSTRACT FROM AUTHOR]