Investigating the effects of input motion uncertainty on ground response analysis

Ground response analysis investigates the effects of local soil conditions on the response of a site during earthquakes. Previous studies have shown that consideration of nonlinear soil behavior is the most realistic method for modeling and analyzing ground response. The dynamic response of a site, in addition to its soil layer’s properties, largely depends on earthquake characteristics. On the other hand, as a result of the complex nature of the earthquake waves’ formation and their travel paths, the earthquakes and their characteristics are essentially random. Also, due to the lack of high magnitude earthquakes in a particular site, it is necessary to use methods for generating artificial earthquakes with logical and near-realistic properties. This paper attempts to produce artificial accelerograms compatible with actual earthquake records based on a generalized nonstationary Kanai–Tajimi model. Then in order to investigate the impacts of uncertainty in the input motions on the seismic ground response, a site response analysis is conducted for a considered soil profile induced by these synthetic earthquakes. For this purpose, a computer program is provided in which a fully nonlinear time domain analyses are carried out for several artificial earthquake accelerograms of varying intensities. The results of this study are presented as stochastic spectral diagrams and non-deterministic responses at the ground surface. These results show that the input motion has a significant effect on the seismic ground response.

Keywords:

Ground response analysis , Nonlinear soil behavior , Extended Masing criteria , Stochastic analysis , artificial earthquake accelerograms.