利用接收函数计算地壳各向异性的可靠性分析及倾斜界面的影响*

使用接收函数研究壳幔速度间断面和速度结构已是常用的技术,但介质各向异性或倾斜的莫霍(Moho)界面,都会造成接收函数波形的复杂性。本文利用远震P波接收函数计算台站下方的地壳各向异性,通过信噪比测试和谐波分析两种方法来验证各向异性结果的可靠性。通过甘肃地震台网的两个台站记录,讨论各向异性和倾斜界面对接收函数的影响,结果显示,台站BYT(白银)下方具有各向异性,而台站WYT(渭源)下方由于可能存在倾斜界面,得到的各向异性结果则有待进一步分析。为了更好地认识倾斜界面对各向异性计算结果的影响,采用合成理论地震图,计算接收函数,然后利用合成接收函数进行各向异性分析。结果表明,计算得到的快波方向不会受到倾斜界面的影响,但是时间延迟会受到影响。

Reliability Analysis of Crustal Anisotropy from Receiver Functions and Effect of Dipping Interface

It is a very common technique to use receiver function to study velocity discontinuity surface between crust and upper-mantle and velocity structure.However,both anisotropy and dipping Moho can generate complicated waveforms of receiver function.We use P receiver function to determine crustal anisotropy,and then applying the signal-tonoise test and harmonic analysis to verify the reliability of the results.Using two stationsfrom Gansu province,we discuss the influence of anisotropy and dipping interface to the receiver function.It shows that the crust beneath BYT is anisotropic,while because of dipping Moho,the crustal anisotropy beneath WYT remains to be determined.In order to better understand the effect of dipping Moho to anisotropy,we use program to generate synthetic seismogram and compute the receiver function,and then make anisotropy analysis from receiver function obtained.Results show that dipping Moho will not influence the fast direction of anisotropy,but the delay time between fast and slow waves.