Rayleigh 面波ZH比反演地壳方位各向异性的可靠性分析

Rayleigh wave ZH ratio as a new seismic measurement sensitive to the velocity profile in the crust and upper mantle. It has the advantage that it is a single station measurement and only sensitive to the structure beneath the seismic station, thus can be applied to regions with both sparse network and high density arrays. And it has been successful in resolving the crustal and upper mantle structure as well as the crustal azimuthal anisotropy with Rayleigh wave ZH ratio. However, different from the inversion of isotropic structures, the anisotropic structure inversion is more complicated and can be affected by many factors, calling for further investigation in validation of the reliability of crustal azimuthal anisotropy from Rayleigh wave ZH ratio with both numerical experiments and real data observations. Since ray path effects from 3D structure are more significant in teleseismic surface wave propagation, we elected to study the near distance (<500 km) Rayleigh wave ZH ratio. We investigate the effects of azimuthal structure on the ray path and new receiver 3D structure on the pattern of azimuthal variation of the Rayleigh wave ZH ratio through numerical modeling and real data observations.

Rayleigh面波ZH（HV比的倒数）比对地壳上地幔速度随深度变化敏感，同时它不受地震震源复杂性影响，在反演壳幔速度结构方面已经取得了成功的应用、也在方位各向异性反演方面取得了新的进展。然而与速度结构反演不同，基于ZH比的各向异性结构反演受到的影响因素较多，其反演各向异性结构的可靠性还需要从理论和观测两个方面结合起来进行检验。由于远距离地震面波容易受到多路径的影响，而较近距离（<500 km）的噪音互相关面波ZH比反演的结构可能主要受到台站附近的结构影响。本项目将通过数值模拟和实际观测，分析较近距离Rayleigh面波ZH比随方位角变化的特征受方位各向异性和地壳三维速度结构的影响，进而为利用ZH比反演和解释方位各向异性提供参考。

Rayleigh面波ZH比是近些年来逐步受关注的地震观测量，它在壳幔结构成像中具有重要的应用意义。本项目的研究目标是通过数值模拟和实际观测，分析较近距离Rayleigh面波ZH比随方位角变化的特征受方位各向异性和地壳三维速度结构的影响，进而为利用ZH比反演和解释方位各向异性提供参考。在实际研究过程中我们根据项目进展作了适当调整：（1）研究获得了Rayleigh面波ZH比的特征，研究表明Rayleigh面波ZH比对速度随深度变化的长波长特征敏感，对速度界面的敏感性弱，同时对绝对速度约束较弱，我们发展了Rayleigh面波ZH比与体波接收函数联合反演的方法，优势互补，可以获得更好的速度结构；（2）改进了Rayleigh面波ZH比测量的方法，通过相位差、相速度等参数控制了观测的可靠性，提高了观测精度；（3）在研究Rayleigh面波ZH比的同时，提出了体波偏振约束地壳速度结构的新观测量，理论和实际应用证实了新观测量可以在地壳结构成像中具有较好的应用前景。项目发表了两篇国际SCI论文，得到了国际同行的肯定，相关成果在地壳成像中取得了较好的应用。