Two-Dimensional Dynamic Finite Element Simulation of Sedimentary Basin Effects: A Case Study of Dayao

Abstract

The two-dimensional (2D) linear and nonlinear seismic response of the Dayao sedimentary basin in Yunnan was investigated using the dynamic finite element method (FEM).  The key seismic response indicators were analyzed, including the displacement amplification coefficient at soil layer observation points, the spectral ratio (HS/HR) of horizontal and vertical acceleration responses between the sedimentary soil layer and reference bedrock sites (site/reference), and comparative assessments of linear and nonlinear  responses. The results indicate that the horizontal displacement amplification coefficient consistently exceeds its vertical counterpart under SV wave incidence, with maximum values of 4.2 and 2.5, respectively. At incidence angles of 30° and 60°, the vertical amplification coefficient reaches a peak of 3.5, whereas, at 85°, it drops to a minimum value of 0.2. Regarding spectral characteristics, the predominant periods of spectral ratio under SV wave incidence are 0.1~0.4 s in the horizontal direction and 0.2~0.5 s in the vertical direction. Conversely, under P wave incidence, the predominant periods of spectral ratio are 0.2~0.5 s in the horizontal direction and approximately 0.1 s in the vertical direction. Furthermore, under strong seismic motion conditions, the nonlinear acceleration response spectrum within the period range of 0.01~0.4 s is consistently lower than its linear counterpart.

Keywords: basin effects, numerical simulation, nonlinear analysis, amplification coefficient, predominant period