Abstract: Based on the parallel computing cluster platform of ABAQUS, according to the typical stratigraphic profile of downtown area in Suzhou city, a two-dimensional nonlinear analytical model of large-scale deep soft site was established. Comparison of nonlinear seismic effects under artificial seismic wave and far-field ground motion of large earthquake were conducted. The results indicate that: (1) The amplification effect of peak ground acceleration (PGA) under far-field ground motion of large earthquake is especially significant compared with that under artificial seismic wave. There is obvious variability among the PGA of ground surface in different locations due to the horizontal heterogeneity and nonlinearity of ground soils. (2) The deep soft site has a significant filtering effect on the high-frequency ground motion wave whose period is less than 0.3 s. When it is under far-field ground motion, there exists an obvious amplification effect on the long-period seismic wave whose period ranging from 0.85 s to 1.65 s. However, there is also apparent filtering effect on the long-period seismic wave whose period ranging from 2.5 s to 7.0 s. (3) It presents fluctuation phenomenon of PGA distribution with depth and along the lateral direction. There are prominent local focusing effects and filtering reduction phenomenon near the contact surface between different soil layers and in the horizontal heterogeneous soil area; and the PGA amplification effect of soils above 20 m depth is relatively larger than that of other soil layers. (4) Both the spectral characteristics of seismic wave and horizontal heterogeneity of ground soils have obvious influence on the shape of ? spectrum. Besides, three-dimensional curves of spectrum shape those describe the acceleration response spectrum changing with depth are given, which can directly show the soil depth in deep soft site where long and thin underground constructions may occur resonance phenomenon.

Key words: deep soft site, two-dimensional analysis, nonlinear seismic effects, far-field large earthquake, horizontal heterogeneity of site soils, characteristics of long period