Comparison the Different Methods of Seismic Response Analysis in Liquefiable sites against Near and Far-Field Earthquakes

Due to the increasing importance of geomorphologic conditions on the seismic ground response, in this paper the details about the effect of liquefiable soils on seismic ground surface response are discussed. At first, the equivalent linear analysis based on total stress model in the frequency domain are carried out and then the nonlinear analysis based on total stress, effective stress model by the pore water pressure development in time domain are done in order to evaluate the differences between the several types of ground response analysis methods. DEEPSOIL.V5 software is used based on the latest achievements and various techniques in both solution domains. LNG port project in Assaluyeh, situated in south of Iran, is considered as a case study. Due to lack of the real data recorded near-field fault at the project site, the simulated method is used in order to create the artificial earthquake. Also three far-field earthquakes have been selected based on conventional seismic hazard studies for the seismic ground response analysis. Then, in order to the better understanding of the obtained responses, the resulted responses spectra are compared with the acceleration design spectra provided in the some valid codes. The result of this study indicates that the pulse effect in the horizontal component of acceleration perpendicular to the fault plane direction, affects severely the surface ground response of the near-field earthquake. The obtained results of the nonlinear modeling of the soil with excess pore water pressure build-up in the time-domain are extremely different from those of frequency-domain responses established based on the equivalent linear method. In addition, because of the inherent linearity of equivalent linear analysis which can lead to spurious resonances in ground responses, the peak ground acceleration in the time-domain is lower than the frequency-domain.