Rotational components of ground motion based on wavelet analysis

The rotational components of strong ground motion near faults have differences in the response to the horizontal and vertical pendulums of seismograph, and according to this principle, a method for obtaining the rotational components of ground motion is established using the wavelet anlysis. The local time-frequency characteristics of uncorrected horizontal and vertical earthquake accelerograms using the discrete wavelet transform are discussed. Then a new threshold method, which processes the wavelet coefficients for horizontal earthquake accelerograms, is established to obtain the rotational components of ground motion. Finally, the correctness and precision of the method for obtaining the rotational components using the wavelet analysis is verified through shaking table tests. The results show that the calculated residual tilt displacement of rotational components of ground motion is consistent with the actual one. And the low-frequency part of the horizontal Fourier spectra of ground motion with the rotational component being filtered out is similar to the vertical ones. The correctness of the proposed method is verified through shaking table tests. Compared with the results processed by the Fourier analysis, the wavelet analysis can achieve more accurate results, and it is consistent with the actual situation.