SUMMARY

Traditional two-station ambient noise interferometry estimates the Green’s function between a pair of synchronously deployed seismic stations. Three-station interferometry considers records observed three stations at a time, where two of the stations are considered receiver–stations and the third is a source–station. Cross-correlations between records at the source–station with each of the receiver–stations are correlated or convolved again to estimate the Green’s function between the receiver–stations, which may be deployed asynchronously. We use data from the EarthScope USArray in the western United States to compare Rayleigh wave dispersion obtained from two-station and three-station interferometry. Three three-station interferometric methods are distinguished by the data segment utilized (coda-wave or direct-wave) and whether the source–stations are constrained to lie in stationary phase zones approximately inline with the receiver–stations. The primary finding is that the three-station direct wave methods perform considerably better than the three-station coda-wave method and two-station ambient noise interferometry for obtaining surface wave dispersion measurements in terms of signal-to-noise ratio, bandwidth, and the number of measurements obtained, but possess small biases relative to two-station interferometry. We present a ray-theoretic correction method that largely removes the bias below 40 s period and reduces it at longer periods. Three-station direct-wave interferometry provides substantial value for imaging the crust and uppermost mantle, and its ability to bridge asynchronously deployed stations may impact the design of seismic networks in the future.

中文翻译：

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三站式干涉仪和层析成像：尾声与直接波

概要

传统的两站式环境噪声干涉测量法估计一对同步部署的地震台站之间的格林函数。三站干涉测量法考虑一次同时观测三个站的记录，其中两个站被视为接收机站，第三个站是源站。将源站与每个接收站之间的记录之间的互相关进行关联或再次卷积，以估计接收站之间的格林功能，这可以异步部署。我们使用来自美国西部EarthScope USArray的数据来比较从两站和三站干涉仪获得的瑞利波色散。三种三站干涉测量方法的区别在于所使用的数据段（苏打波还是直接波），以及源站是否被限制在与接收站大致成一直线的固定相位区域内。主要发现是，在获得信噪比，带宽和噪声方面的表面波色散测量结果时，三站直达波方法的性能明显优于三站柯达波方法和两站环境噪声干涉测量法。获得的测量数量，但相对于两站干涉仪而言偏差较小。我们提出了一种射线理论校正方法，该方法可以在40 s周期以下大幅度消除偏差，并在较长的周期内减小偏差。