Quantifying the edge-induced seismic aggravation in shallow basins relative to the 1D SH modelling

Basin effects have long been proven to be of significance to seismic ground motions. However, 1D site response analysis, especially based on the equivalent nonlinear method, dominates engineering practice. In this paper, we aim to quantify the edge-induced aggravation in shallow sedimentary basins in addition to the 1D site effects. We chose a fixed shape for all shallow basins. Vertical heterogeneities are configured based on 31 KiK-net site profiles, complemented by another 19 hypothetic soil profiles. We then simulate both the 1D and 2D ground motions of each basin subjected to nine earthquake records modelled as vertically propagating SH waves. We use the aggravation factor, the ratio of 2D to 1D response spectra, to characterize the additional amplification induced by the lateral heterogeneity. Our results indicate that, for shallow basins, it is the region close to the basin edge that experiences the most significant aggravation, increasing 1D amplification by a factor between 1.2 and 1.5 mainly within the period band from 0.1 s to Th, where Th is the 1D fundamental resonance period at the basin centre.