不同震源入射角对海底盆地地震响应的影响

Impact of Different Source Incidence Angles on Seismic Response of Submarine Basin

为研究地震作用对海底盆地的影响,在分析网格大小和PML边界厚度对计算精度影响的基础上,综合考虑了海水、盆地内不规则地形以及多层介质等因素,运用谱元法理论建立了礼乐盆地地震动分析二维模型,研究了盆地在不同震源入射角下的响应。结果表明:在考虑流固耦合的情况下,网格尺寸为四分之一波长时即可取得较高精度,PML边界厚度至少为2个波长时方可达到理想效果。震源的不同会影响放大系数的大小及频谱特征。当地震波从盆地中部入射时,随着震源入射角的增大,放大系数逐渐减小;在不同震源入射角下,盆地不同位置的加速度时程及频谱特征差异较大。当地震波从左侧入射时,放大系数的分布规律与地震波从盆地中部入射时有所不同;在不同的震源入射角下,盆地不同位置的加速度时程及频谱特征差异较小。在研究盆地地震相关问题时,海水、地形以及多层介质的影响是不可忽视的。

In order to study the influence of seismic action on the submarine basin,based on the analysis of the influence of grid size and PML boundary thickness on the calculation accuracy,a two-dimensional seismic analysis model of the Lile basin is established by using the spectral element method,taking into account the factors of seawater,irregular topography in the basin and multi-layer media,and the response of the basin at different incident angles of earthquake sources is studied.The results show that high accuracy can be achieved when the mesh size is a quarter wavelength and the PML boundary thickness is at least two wavelengths when considering the fluid-solid coupling.The magnification factor and spectrum characteristics are influenced by the source.When seismic waves are incident from the middle of the basin,the amplification coefficient decreases with the increase of the incident angle of the source.Acceleration time history and frequency spectrum characteristics differ greatly in different locations of the basin at different source incidence angles.When the seismic wave is incident from the left side,the distribution law of the amplification coefficient is different from that when the seismic wave is incident from the middle of the basin.Acceleration time history and spectrum characteristics differ slightly in different locations of the basin at different source incidence angles.The influence of seawater,topography and multi-layered media can not be ignored in the study of basin earthquake-related problems.