The prediction of seismic amplification effect in three-dimensional sedimentary basins and its application

Numerous studies have shown that the basin amplification effect is influenced by characteristic parameters such as basin geometry and media impedance contrast, but quantitative analysis of the effect for three-dimensional (3D) basins is still rare. In this paper, the basin amplification effect is quantified through an aggravation factor (AGF ), which is defined as the ratio between 3D and 1D acceleration response spectra along the basin surface. Considering the 3D geometry of the actual basin, we investigate the sensitivity of aggravation factors to inclination angles, shape ratios, and impedance contrasts by establishing 78 3D trapezoidal sedimentary basin models with different characteristic parameters. Furthermore, we perform a statistical analysis of the aggravation factors and propose their prediction formulas, which are applied to the Euroseistest basin and the Shidian basin. The above analysis reveals that: (1) The effects of inclination angle and shape ratio on the aggravation factor are concentrated in the edge part and central part of the basin, respectively, while the impedance contrast has less influence on the aggravation factor along the basin surface; (2) From the prediction results for the Euroseistest basin, the aggravation factor of the 3D model is higher than that of the 2D model with a maximum error of 22%, while the distribution pattern of the aggravation factor along the surface is similar; and (3) The predicted results for the Shidian basin show that the basin with a small inclination angle has a larger aggravation factor in the edge part and even exceeds the central part; for example, the highest aggravation factor is 2.155 in the edge part of the basin with an inclination angle of 6°.