The versatility and cost efficiency of fibre-optic distributed acoustic sensing (DAS) technologies facilitate geophysical monitoring in environments that were previously inaccessible for instrumentation. Moreover, the spatio-temporal data density permitted by DAS naturally appeals to seismic array processing techniques, such as beamforming for source location. However, the measurement principle of DAS is inherently different from that of conventional seismometers, providing measurements of ground strain rather than ground motion, and so the suitability of traditional seismological methods requires in-depth evaluation. In this study, we evaluate the performance of a DAS array in the task of seismic beamforming, in comparison with a co-located nodal seismometer array. We find that, even though the nodal array achieves excellent performance in localising a regional M_L 4.3 earthquake, the DAS array exhibits poor waveform coherence and consequently produces inadequate beamforming results that are dominated by the signatures of shallow scattered waves. We demonstrate that this behaviour is likely inherent to the DAS measurement principle, and so new strategies need to be adopted to tailor array processing techniques to this emerging measurement technology. One strategy demonstrated here is to convert the DAS strain rates to particle velocities by spatial integration using the nodal seismometer recordings as a reference, which dramatically improves waveform coherence and beamforming performance and warrants new types of “hybrid” array design that combine dense DAS arrays with sparse seismometer arrays.

中文翻译：

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评估分布式声感测阵列的地震波束形成能力

光纤分布式声学传感（DAS）技术的多功能性和成本效益有助于在以前无法使用仪器的环境中进行地球物理监测。此外，DAS允许的时空数据密度自然吸引了地震阵列处理技术，例如用于震源定位的波束成形。但是，DAS的测量原理与传统的地震仪固有地不同，它提供的是地面应变而非地面运动的测量，因此传统地震学方法的适用性需要深入评估。在这项研究中，我们与同位节点地震仪阵列相比，评估了DAS阵列在地震波束成形任务中的性能。我们发现中号_大号 4.3地震，DAS阵列展现出差的波形的一致性，并因此产生由浅散射波的签名支配波束形成不充分的结果。我们证明这种行为可能是DAS测量原理固有的，因此需要采用新的策略来调整阵列处理技术以适应这种新兴的测量技术。此处展示的一种策​​略是通过使用节点地震仪记录作为参考通过空间积分将DAS应变速率转换为粒子速度，这可以显着改善波形相干性和波束形成性能，并保证将密集DAS阵列与高密度DAS阵列相结合的新型“混合”阵列设计。稀疏地震仪阵列。