Array methods like spatial auto-correlation (SPAC) method and the centerless circular array (CCA) method have provided a convenient means of inferring the phase velocity of surface waves. However, these methods are under the assumption of horizontally layered medium (lateral homogeneity) while the ground structure is actually likely to be inclined. Hence, it is expected to obtain more detailed information of ground structure such as inclination by making better use of the records. In recent years, the seismic interferometry theory has also been widely used to estimate ground structure. According to seismic interferometry theory, the cross correlation of motion between two sites is proportional to the imaginary part of the Green’s function (IOG) between the two sites in diffuse wavefield. In this study, we can obtain the ratio of IOG between two sites by taking the ratio of power spectra between the same two sites. We propose this ratio as an indicator of the lateral heterogeneity between two sites. Through numerical simulation and a field test, we demonstrate that the significance of ratio of power spectra can be interpreted from the sight of ratio of IOG successfully.

中文翻译：

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应用阵列方法对两个位点之间功率谱垂直分量比的新意义。

像空间自相关（SPAC）方法和无心圆阵列（CCA）方法这样的数组方法提供了一种方便的方法来推断表面波的相速度。但是，这些方法是在水平分层介质（横向同质性）的假设下，而地面结构实际上可能会倾斜。因此，期望通过更好地利用记录来获得诸如倾斜的地面结构的更详细的信息。近年来，地震干涉法理论也被广泛用于估算地面结构。根据地震干涉理论，两个站点之间运动的互相关与弥散波场中两个站点之间格林函数（IOG）的虚部成比例。在这项研究中，我们可以通过获取两个站点之间的功率谱比率来获得两个站点之间的IOG比率。我们建议使用该比率作为两个站点之间横向异质性的指标。通过数值模拟和现场测试，我们证明可以从IOG比率的角度成功地解释功率谱比率的重要性。