Statistical analysis of the additional amplification in deep basins relative to the 1D approach

To bridge the 1D to the multidimensional site response analysis, aggravation factor at a certain surface point is defined as the ratio of its response spectrum computed using a multidimensional model to that computed using its local 1D model. Zhu et al. (2017a) quantified the aggravation factor in 2D shallow basins. As an extension to Zhu et al. (2017a), this paper aims to quantify, in a statistical sense, the aggravation factor in 2D deep basins using the numerical approach. We thus configure a total of 32 heterogeneous deep basin formations (half-width less than approximately five times basin depth) constructed based mainly on real 1D soil profiles. Nine seismic motions recorded on rock site are taken as vertically propagating SH waves. Both 1D and 2D ground motions of each basin model are simulated and averaged over the nine input motions. 2D ground motions in these deep basins are found to be significantly aggravated relative to 1D results within the period range from 0.1 s to T_h across the whole basin width by a factor of which the 16th and 84th percentile are 1.3 and 1.8 respectively (T_h is the fundamental period of the soil column at the deepest portion of a basin).