Numerical modeling of seismic site effects in a shallow estuarine bay (Suai Bay, Shantou, China)

摘要

This paper presents the results of numerical modeling of seismic site effects in a shallow estuarine bay (Suai Bay, Shantou, China), which is meaning for seismic hazard assessment and mitigation of estuarine and coastal structures, such as immersed tunnels, pipelines, caissons and breakwaters. The subsurface stratum and soil properties in the study area are obtained from geological and geotechnical surveys. Large-scale 2D finite-element refined nonlinear modeling is used to simulate ground motion for near-field and far-filed input motions with different design earthquake levels. The results show that for the study area: (1) The spatial distribution of PGA amplification factor presents obvious vertical and horizontal variations and is strongly affected by the overall geometry of interfaces of different materials. (2) The attenuation in soft sediments have significant influences on surface ground motion, which leads to a deamplification of the acceleration amplitude, a prolongation of the significant duration and a filtration of the high-frequency spectral content. (3) The PGA alone cannot be regarded as an adequate parameter to quantify nonlinear site effects, while the energy content (expressed by Arias intensity) is more closely related to transfer functions patterns. (4) The seismic intensity at surface is greater than the intensity of input motion during weak motions, while the seismic intensity at surface is smaller than the intensity of input motion during strong motions, suggesting that isolation effects may be expected in the areas having thick soft soils with a low plasticity index during strong motions.