Three-station interferometry and tomography: coda versus direct waves
Three-station interferometry and tomography: coda versus direct waves
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DOI：
10.1093/gji/ggaa046
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发表时间：
2020-04
影响因子：
2.8
通讯作者：
Shane Zhang;Lili Feng;M. Ritzwoller
中科院分区：
文献类型：
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作者：
Shane Zhang;Lili Feng;M. Ritzwoller
传统的双站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。三站干涉测量法一次考虑三个台站所观测到的记录，其中两个台站被视为接收台站，第三个是源台站。源台站记录与每个接收台站记录之间的互相关再次进行相关或卷积，以估计接收台站之间的格林函数，这些接收台站可以异步部署。我们利用美国西部地球透镜计划（EarthScope USArray）的数据来比较双站和三站干涉测量法所得到的瑞利波频散。三种三站干涉测量方法根据所使用的数据段（尾波或直达波）以及源台站是否被限制在大致与接收台站成直线的稳定相位区内而有所不同。主要发现是，在信噪比、带宽以及所获得的测量数量方面，三站直达波方法在获取面波频散测量值上比三站尾波方法和双站环境噪声干涉测量法表现得好得多，但相对于双站干涉测量法存在较小偏差。我们提出一种射线理论校正方法，该方法在很大程度上消除了40秒周期以下的偏差，并在更长周期减小了偏差。三站直达波干涉测量法对地壳和最上部地幔成像具有重要价值，并且其连接异步部署台站的能力可能会影响未来地震台网的设计。
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.