基于谱元法的三维盆地－子盆地共振初步研究

本文基于谱元法，模拟三种深度的点震源下，四种倾角的三维单一小盆地模型和盆地－子盆地模型的地震动，通过盆地模型和基岩半空间模型的傅氏谱比分析三维盆地－子盆地模型的共振频率和放大特性。结果表明:（1）盆地－子盆地模型下，外部大盆地的存在导致子盆地共振频率下降约5%，盆地倾角的增大导致子盆地的共振频率略微减小。三维子盆地的共振频率约为二维模型的1.5倍左右。（2）子盆地模型相对于基岩半空间的放大倍数随着盆地形状比降低而增加。形状比由0.88降低至0.5，子盆地的放大系数增大1.3－1.8倍左右。（3）盆地－子盆地模型相对于单一小盆地模型的放大随震源深度的增加而降低，震源深度由2 km增加到18 km，由2.3降至1.3。

Preliminary study on three-dimensional basin-and-sub basin resonance based on spectral element method

Based on the spectral element method,three different depths ground motion of three-dimensional Small Basin model(SB)and Basin-and-Sub basin model(BSB)with four dip angles under the action of point sourcearesimulated,and the three-dimensional resonance frequency and spectrum amplification is analyzedthrough the fourier spectrum ratio of basin model and bedrock half space model. The results show that:① Under the Basin-and-Sub basin model,the existence of large external basins leads to a decrease in resonance frequency of about 5%,and the increase of basin dip angle also lead to the slight decrease of the resonance frequency of Small Basin. The three-dimensional resonance frequency is about 1.5 times that of two-dimensional.②The magnification of Basin-and-Sub basin model relative to bedrock half space increases with the decrease of basin shape ratio. The shape ratio decreases from 0.88 to 0.5,and the magnification factor of the sub basin increases by about 1.3-1.8 times.③ The amplification of Basin-and-Sub basin model relative to single Small Basin model decreases with the increase of focal depth,which increases from 2km to 18km and decreases from 2.3 to 1.3.