Rapid deployment of distributed acoustic sensing systems to track earthquake activity

Karrenbach, Martin; Shen, Zhao; Li, Zefeng; Cole, Steve; Williams, Ethan; Klesh, A. T.; Wang, Xin; Zhan, Zhongwen; LaFlame, Lisa; Yartsev, Victor; Bogdanov, Vlad

doi:10.1190/segam2020-3426905.1

Cited by 4 publications

(3 citation statements)

References 6 publications

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“…While most original application of DAS was in industry, where the spatial resolution and high environmental tolerance of fibre-optic cable makes DAS eminently suitable for borehole deployment, the falling costs of the interrogator units and the increasing utilization of 'dark fibre' (already laid inactive telecom fibre) have made surface deployments an attractive proposition for fundamental research purposes. Recent studies have shown that onshore DAS can detect both teleseismic (Lindsey et al 2017;Yu et al 2019) and local (Wang et al 2018;Karrenbach et al 2020;Zhan 2020) earthquakes with waveforms that match colocated seismometers. Several studies utilizing offshore cables have also reported success in observations of both earthquakes and ambient environmental seismology (Lindsey et al 2019;Sladen et al 2019;Williams et al 2019;Spica et al 2020;Ide et al 2021;Matsumoto et al 2021).…”

Section: Introductionmentioning

confidence: 99%

“…The wavefield representation offers a simple and coherent mechanism for converting between strains and displacements, which makes it especially well suited for studying the lateral variations of DAS amplitude response. Characterization of this response will be essential for realizing the promise of DAS as a spatially dense sensing modality for strong ground motions and earthquake early warning (Karrenbach et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Wavefield-based evaluation of DAS instrument response and array design

Muir

Zhan

2021

Geophysical Journal International

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Summary Distributed Acoustic Sensing (DAS) networks promise to revolutionize observational seismology by providing cost-effective, highly dense spatial sampling of the seismic wavefield, especially by utilizing pre-deployed telecomm fiber in urban settings for which dense seismic network deployments are difficult to construct. However, each DAS channel is sensitive only to one projection of the horizontal strain tensor and therefore gives an incomplete picture of the horizontal seismic wavefield, limiting our ability to make a holistic analysis of instrument response. This analysis has therefore been largely restricted to pointwise comparisons where a fortuitious coincidence of reference three-component seismometers and co-located DAS cable allows. We evaluate DAS instrument response by comparing DAS measurements from the PoroTomo experiment with strain-rate wavefield reconstructed from the nodal seismic array deployed in the same experiment, allowing us to treat the entire DAS array in a systematic fashion irrespective of cable geometry relative to the location of nodes. We found that, while the phase differences are in general small, the amplitude differences between predicted and observed DAS strain-rates average a factor of 2 across the array and correlate with near-surface geology, suggesting that careful assessment of DAS deployments is essential for applications that require reliable assessments of amplitude. We further discuss strategies for empirical gain corrections and optimal placement of point sensor deployments to generate the best combined sensitivity with an already deployed DAS cable, from a wavefield reconstruction perspective.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Wavefield-based evaluation of DAS instrument response and array design

Muir

Zhan

2021

Geophysical Journal International

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“…DAS can provide dense, wide bandwidth, and continuous long-duration seismic recordings with spatial resolutions of a few meters over distances of a few tens of kilometers (Daley et al, 2013;Daley et al, 2016), which can be used for noise cross-correlation and high-resolution surface-wave imaging. Extensive pre-existing networks of unused subsurface fiber-optic cables known as dark fiber can also be used for this purpose (Jousset et al, 2018;Ajo-Franklin et al, 2019;Wang et al, 2020;Karrenbach et al, 2020;Zhu et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Measurement of Surface-Wave Phase-Velocity Dispersion on Mixed Inertial Seismometer – Distributed Acoustic Sensing Seismic Noise Cross-Correlations

Nayak

Ajo‐Franklin

2021

Bulletin of the Seismological Society of America

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The application of ambient seismic noise cross-correlation to distributed acoustic sensing (DAS) data recorded by subsurface fiber-optic cables has revolutionized our ability to obtain high-resolution seismic images of the shallow subsurface. However, passive surface-wave imaging using DAS arrays is often restricted to Rayleigh-wave imaging and 2D imaging along straight segments of DAS arrays due to the intrinsic sensitivity of DAS being limited to axial strain along the cable for the most common type of fiber. We develop the concept of estimating empirical surface waves from mixed-sensor cross-correlation of velocity noise recorded by three-component seismometers and strain-rate noise recorded by DAS arrays. Using conceptual arguments and synthetic tests, we demonstrate that these cross-correlations converge to empirical surface-wave axial strain response at the DAS arrays for virtual single step forces applied at the seismometers. Rotating the three orthogonal components of the seismometer to a tangential–radial–vertical reference frame with respect to each DAS channel permits separate analysis of Rayleigh waves and Love waves for a medium that is sufficiently close to 1D and isotropic. We also develop and validate expressions that facilitate the measurement of surface-wave phase velocity on these noise cross-correlations at far-field distances using frequency–time analysis. These expressions can also be used for DAS surface-wave records of active sources at local distances. We demonstrate the recovery of both Rayleigh waves and Love waves in noise cross-correlations derived from a dark fiber DAS array in the Sacramento basin, northern California, and nearby permanent seismic stations at frequencies ∼0.1–0.2 Hz, up to distances of ∼80 km. The phase-velocity dispersion measured on these noise cross-correlations are consistent with those measured on traditional noise cross-correlations for seismometer pairs. Our results extend the application of DAS to 3D ambient noise Rayleigh-wave and Love-wave tomography using seismometers surrounding a DAS array.

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