PL波频散特征及其在岩石圈P波速度结构成像中的应用

面波成像是地球物理成像的最重要技术手段之一。经典的面波成像方法主要通过瑞雷波和勒夫波的频散信息反演S波速度结构。除了对应于本征振型的瑞雷波和勒夫波之外，对应于漏能振型的PL波也是一种具有频散特征的波。由于PL波理论的复杂性，至今通过PL波频散进行成像的研究仍然接近空白。最近，申请人通过频率贝塞尔变换法成功地从天然地震的PL波记录中提取出高频多阶频散曲线，并在理论分析中发现了除漏能振型外的另外一组控制PL波频散的频散曲线：伪声波振型。通过其敏感性分析，我们发现伪声波振型对于岩石圈的P波速度结构具有很强的敏感性。伪声波振型和漏能振型的耦合则可以有效地解释和预测PL波频散。本课题拟在上述研究成果的基础之上，实现对于PL波频散的自动分类，并通过对分类得到的伪声波振型反演以获取高精度岩石圈P波速度结构。预期成果对提高面波成像方法的约束力，尤其是增强对于岩石圈P波速度结构的约束力具有重要意义。

Surface wave imaging is one of the most important technical of geophysical imaging. The classical surface wave imaging methods mainly use the dispersion information of Rayleigh and Love wave to invert the shear velocity structure. In addition to Rayleigh and Love wave, the PL waves which are corresponding to the leaking modes also exhibit dispersion characteristics. However, due to the complexity of PL wave theory, the PL dispersion is rarely used for imaging. Recently, we successfully extracted high-frequency multiple PL dispersion curves from earthquake records through the Frequency-Bessel Transform (F-J) Method and found that there are another group of dispersion curves (pseudoacoustic mode) that control the PL dispersion in addition to leaking mode. Through the sensitivity analysis, we found that the pseudoacoustic mode has a strong sensitivity to the P-wave velocity structure of the lithosphere. The coupling of pseudoacoustic mode and leaking mode can effectively explain and predict the dispersion of PL waves. This project intends to realize the automatic classification of PL wave dispersion and inversion of P-wave velocity structure by the pseudoacoustic mode, on the basis of previous progresses. The expected results are of significance for improving the constraints of surface wave imaging method, especially for the constraints on the P-wave velocity structure of the lithosphere.