Distributed Acoustic Sensing of Strain at Earth Tide Frequencies

Becker, Matthew W.; Coleman, Thomas

doi:10.3390/s19091975

Cited by 31 publications

(20 citation statements)

References 23 publications

(31 reference statements)

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“…The present DAS measurement indicates enough sensitivity in the low frequency range down to , and supports the possibility of detection of such long-period phase changes in a fiber-optic cable. It has been reported that a long-period strain oscillation induced by the earth tide can be detected by DAS, albeit being performed in a laboratory experiment 47 .…”

Section: Resultsmentioning

confidence: 99%

Detection of hydroacoustic signals on a fiber-optic submarine cable

Matsumoto

Araki

Kojima

et al. 2021

Sci Rep

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A ship-based seismic survey was conducted close to a fiber-optic submarine cable, and 50 km-long distributed acoustic sensing (DAS) recordings with air-gun shots were obtained for the first time. We examine the acquired DAS dataset together with the co-located hydrophones to investigate the detection capability of underwater acoustic (hydroacoustic) signals. Here, we show the hydroacoustic signals identified by the DAS measurement characterizing in frequency-time space. The DAS measurement can be sensitive for hydroacoustic signals in a frequency range from $$10^{-1}\,\text {Hz}$$ 10 - 1 Hz to a few tens of Hz which is similar to the hydrophones. The observed phases of hydroacoustic signals are coherent within a few kilometers along the submarine cable, suggesting the DAS is suitable for applying correlation analysis using hydroacoustic signals. Although our study suggests that virtual sensor’s self-noise of the present DAS measurement is relatively high compared to the conventional in-situ hydroacoustic sensors above a few Hz, the DAS identifies the ocean microseismic background noise along the entire submarine cable except for some cable sections de-coupled from the seafloor.

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Section: Resultsmentioning

confidence: 99%

Detection of hydroacoustic signals on a fiber-optic submarine cable

Matsumoto

Araki

Kojima

et al. 2021

Sci Rep

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“…The broadband nature of DAS has largely been overshadowed by the use of DAS in active‐source experiments at high frequencies (

f > 10

Hz;

T < 0.1

s). The long‐period frequency response of the DAS method has been demonstrated in recordings of teleseismic earthquakes (Ajo‐Franklin et al, ; Jousset et al, ) and laboratory and field pump tests (Becker et al, ; Becker & Coleman, ). To date, the longest period earthquake signal observed with DAS used a dark fiber DAS array in the Mojave Desert to capture propagating surface waves down to

T = 200

s (Yu et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…To date, the longest period earthquake signal observed with DAS used a dark fiber DAS array in the Mojave Desert to capture propagating surface waves down to

T = 200

s (Yu et al, ). Recently, Becker and Coleman () showed that DAS can record tidal periods (

T = 4.3 \times 1 0^{4}

s) in a laboratory setting, albeit with a strain amplitude

7 \times 1 0^{3}

times greater than the solid Earth tide.…”

Section: Introductionmentioning

confidence: 99%

On the Broadband Instrument Response of Fiber‐Optic DAS Arrays

2020

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Distributed Acoustic Sensing (DAS) is a novel tool in array seismology that measures the phase of backscattered laser pulses traveling in a fiber‐optic cable, and relates this measurement to the axial strain induced on the cable by a propagating seismic wavefield. Combining DAS with telecommunications optical fiber networks has begun to address a range of earth science questions where cost and field logistics have historically hindered observations. Unlike classic inertial seismometers, DAS instrument response is presently unquantified. This topic includes a variable sensing element—the fiber, including packaging and installation—which changes between experiments. Ignoring this element, one DAS record should approximate a fixed‐length strain gauge, which exactly measures Earth's motion down to quasi‐static frequencies relevant to geodesy. In this paper, we test this hypothesis using seismological observations of teleseismic earthquakes and microseism noise spanning the 1 to 120 s period range. We use a commercial DAS interrogator unit connected to an optical fiber previously used for telecommunication and a colocated broadband seismometer to estimate the DAS transfer function. We find a 1:1 correspondence with actual ground motion from 10–120 s. At shorter periods (1–10 s), DAS amplitude response is enhanced by 3–11 dB. Phase response is flat over this range of periods. We interpret the recovered DAS response function in terms of hypothesized fiber coupling and photonic effects. We propose this calibration methodology for future DAS experiments where seismic amplitude information is desired.

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“…In general, the instrument response of DAS is broader than that of traditional receivers. However, it requires careful treatment and calibration as the fiber properties, casing, and installation method can influence it [31,[48][49][50]. A virtual DAS receiver is a single-axis measurement sensor, which is sensiti strain (or strain-rate) along the direction of the fiber.…”

Section: Introductionmentioning

confidence: 99%

Seismic Applications of Downhole DAS

Lellouch

Biondi

2021

Sensors

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Distributed Acoustic Sensing (DAS) is gaining vast popularity in the industrial and academic sectors for a variety of studies. Its spatial and temporal resolution is ever helpful, but one of the primary benefits of DAS is the ability to install fibers in boreholes and record seismic signals in depth. With minimal operational disruption, a continuous sampling along the trajectory of the borehole is made possible. Such resolution is highly challenging to obtain with conventional downhole tools. This review article summarizes different seismic uses, passive and active, of downhole DAS. We emphasize current DAS limitations and potential ways to overcome them.

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Distributed Acoustic Sensing of Strain at Earth Tide Frequencies

Cited by 31 publications

References 23 publications

Detection of hydroacoustic signals on a fiber-optic submarine cable

Detection of hydroacoustic signals on a fiber-optic submarine cable

On the Broadband Instrument Response of Fiber‐Optic DAS Arrays

Seismic Applications of Downhole DAS

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