TI介质中地震波旋转运动特性研究

The study on rotational motion of seismic wave in TI media

地震波的旋转运动研究是地球动力学中的一个新兴领域.本文基于弹性波理论推导出旋转速度与相速度的关系,通过Kelvin-Christoffel方程推导了TI介质中地震波相速度的计算公式,从而得到TI介质中的Thomsen参数与旋转速度之间关系;继而借助于几个典型的TI介质模型模拟了地震波旋转运动.模拟结果显示:qP波旋转速度随着ε、δ的增加逐渐增大;qSV波旋转速度随着ε的增大而减小,随δ增大而增大;qSH波旋转速度随γ、δ的增加而增大,且γ的影响更大.另外,从相速度与旋转速度对比发现:qP波和qSH波旋转速度即不是圆形也不是椭圆,相对于相速度更具有方向性,这说明相对于平移运动,旋转运动的信息更有方向性和各向异性.

Rotational motion of seismic wave is an emerging field of geodynamics.Based on elastic wave theory,this paper derived the relationship between rotation rate and phase velocity,and obtained the phase velocity of seismic wave in TI medium by solving Kelvin-Christoffel equation and relationship between Thomsen parameters of the elastic medium and rotation rate.We computed the peak rotation rates and phase velocity of qP-waves,qSV-waves,qSH-waves generated in different TI materials.The result indicate that qP rotation rates are higher with increasing values ofεandδ,qSH rotation rates are higher with increasing values ofγandδ,qSV rotation rates are higher with increasing values ofδ but decrease with increasing values ofε.Through the comparison of the phase velocity and rotational rate,pointed out rotational motion has better directivity and anisotropy than translation motion.