We demonstrate the feasibility of finite frequency ambient noise tomography (ANT) in mapping broadband surface wave phase velocities in the western United States using data from the USArray. We obtain cross‐correlation functions (CCFs) of ambient noise data between pairs of stations and then construct a 2‐D phase sensitivity kernel for each CCF between a pair of stations by treating one station as a “virtual” point source and the other as the receiver. Based on a standard, iterative, linearized inversion technique, we develop a finite frequency ANT method and use this method to construct phase velocity maps. These phase velocity maps are very similar to other reported maps generated by established tomography methods based on ray theory at short periods. At intermediate and long periods (>40 s), phase velocity maps based on finite frequency ANT significantly differ from those based on ray theory ANT; however, they are similar with those based on Helmholtz tomography which uses earthquake surface wave data and considers finite frequency effects of surface waves. Our results suggest that finite frequency effects need to be considered in intermediate‐ and long‐period ANT if one intends to resolve upper‐mantle structures with subwavelength scales using ANT.

中文翻译：

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宽带有限频率环境噪声层析成像：美国西部使用USArray电台的案例研究

我们展示了有限频率环境噪声层析成像（ANT）在使用来自USArray的数据绘制美国西部宽带表面波相位速度时的可行性。我们获得站点对之间的环境噪声数据的互相关函数（CCF），然后通过将一个站点视为“虚拟”点源，将另一个站点视为“虚拟”点源，为一对站点之间的每个CCF构造一个二维相位灵敏度内核。收件人。基于一种标准的，迭代的，线性化的反演技术，我们开发了一种有限频率的ANT方法，并使用该方法来构建相速度图。这些相速度图与通过基于射线理论的已建立的层析成像方法在短期内生成的其他报告图非常相似。在中长期（> 40 s），基于有限频率ANT的相速度图与基于射线理论ANT的相速度图明显不同。但是，它们与基于Helmholtz层析成像的方法相似，后者使用地震表面波数据并考虑了表面波的有限频率效应。我们的结果表明，如果要使用ANT解析具有亚波长尺度的上地幔结构，则在中长期ANT中需要考虑有限的频率效应。