Seismic response analysis of a multi-layered sedimentary valley in a layered half-space in time domain

The two-dimensional seismic responsein time domain of a multi-layered sedimentary valley was investigated by using a multi-domain indirect boundary element method (IBEM). In the approach, the seismic response was calculated in frequency domain firstly, and then the results in frequency-domain calculations were superposed and transformed back into time-domain by the fast Fourier transform method. In the multi-domain IBEM, the full-space Green's functions and the layered half-space Green's functions were used to construct scattered wave fields in the sediment enclosed domain and in the open semi-infinite space domain respectively. This method can inherit the advantages of both Green's functions. On the basis of verifying the validity of the method, the numerical results of typical layered valleys under incident El Centro wave were provided and the effect of the variation of sedimentary sequence on the peaks and response spectrum of the seismic ground motion nearby the valley was focused. The results show that the variation of sedimentary sequence leads to observable differences in the seismic accelerations and the seismic response spectra. Specifically, when sedimentary layers are in normal sequence, the seismic acceleration peak is the largest, while the corresponding response spectrum peak period is the smallest. When sedimentary layers are in inverted sequence, the seismic acceleration peak is the smallest, while the corresponding response spectrum peak period is the largest. In addition, inverted-sequence sediment weakens the energy of the intermediate and high frequency waveband. Comparing with normal-sequence sediment, inverted-sequence sediment appears to be of good shock insulation effect. © 2020, Editorial Office of Journal of Vibration and Shock. All right reserved.