scholarly journals Distributed Acoustic Sensing for Near Surface Imaging from Submarine Telecommunication Cable: Case Study in the Trondheim Fjord

2021 ◽  
Author(s):  
Kittinat Taweesintananon ◽  
Martin Landrø ◽  
Jan Kristoffer Brenne ◽  
Aksel Haukanes
Keyword(s):  
Surface Imaging ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Telecommunication Cable ◽  
Distributed Acoustic Sensing

scholarly journals Distributed Acoustic Sensing for Seismic Monitoring of The Near Surface: A Traffic-Noise Interferometry Case Study

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Shan Dou ◽  
Nate Lindsey ◽  
Anna M. Wagner ◽  
Thomas M. Daley ◽  
Barry Freifeld ◽  
...  
Keyword(s):  
Traffic Noise ◽  
Seismic Monitoring ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Noise Interferometry ◽  
Distributed Acoustic Sensing

Low-frequency Ambient Distributed Acoustic Sensing (DAS): Case Study from Perth, Australia

2021 ◽  
Author(s):  
Jeffrey Shragge ◽  
Jihyun Yang ◽  
Nader Issa ◽  
Michael Roelens ◽  
Michael Dentith ◽  
...  
Keyword(s):  
Surface Wave ◽  
Optical Fiber ◽  
Low Frequency ◽  
Wave Analysis ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Geotechnical Investigations ◽  
Wide Range ◽  
Distributed Acoustic Sensing

Summary Ambient wavefield data acquired on existing (so-called “dark fiber”) optical fiber networks using distributed acoustic sensing (DAS) interrogators allow users to conduct a wide range of subsurface imaging and inversion experiments. In particular, recorded low-frequency (<2 Hz) surface-wave information holds the promise of providing constraints on the shear-wave velocity (VS) to depths exceeding 0.5 km. However, surface-wave analysis can be made challenging by a number of acquisition factors that affect the amplitudes of measured DAS waveforms. To illustrate these sensitivity challenges, we present a low-frequency ambient wavefield investigation using a DAS dataset acquired on a crooked-line optical fiber array deployed in suburban Perth, Western Australia. We record storm-induced microseism energy generated at the nearby Indian Ocean shelf break and/or coastline in a low-frequency band (0.04 − 1.80 Hz) and generate high-quality virtual shot gathers (VSGs) through cross-correlation and cross-coherence interferometric analyses. The resulting VSG volumes clearly exhibit surface-wave energy, though with significant along-line amplitude variations that are due to the combined effects of ambient source directivity, crooked-line acquisition geometry, and the applied gauge length, fiber coupling, among other factors. We transform the observed VSGs into dispersion images using two different methods: phase shift and high-resolution linear Radon transform. These dispersion images are then used to estimate 1-D near-surface VS models using multi-channel analysis of surface-waves (MASW), which involves picking and inverting the estimated Rayleigh-wave dispersion curves using the particle-swarm optimization global optimization algorithm. The MASW inversion results, combined with nearby deep borehole information and 2-D elastic finite-difference modeling, show that low-frequency ambient DAS data constrain the VS model, including a low-velocity channel, to at least 0.5 km depth. Thus, this case study illustrates the potential of using DAS technology as a tool for undertaking large-scale surface-wave analysis in urban geophysical and geotechnical investigations to depths exceeding 0.5 km.

Distributed acoustic sensing for near-surface imaging using submarine telecommunication cable: a case study in the Trondheimsfjord, Norway

Geophysics ◽  
2021 ◽  
pp. 1-69
Author(s):  
Kittinat Taweesintananon ◽  
Martin Landrø ◽  
Jan Kristoffer Brenne ◽  
Aksel Haukanes
Keyword(s):  
Signal To Noise Ratio ◽  
Seismic Source ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Optical Cable ◽  
Distributed Acoustic Sensing ◽  
Hydrophone Array ◽  
Seismic Images ◽  
Data Processing Methods

Distributed acoustic sensing (DAS) transforms submarine telecommunication cables into densely sampled seismic receivers. To demonstrate DAS applications for seismic imaging, we use an optical cable on the seafloor in the Trondheimsfjord, Norway, to record seismic data generated by a controlled seismic source. The data are simultaneously recorded by a towed hydrophone array and the fiber optic cable. Following our data processing methods, we can produce seismic images of the seafloor and underlying geological structures from both hydrophone array and DAS data. We find that the hydrophone and DAS data have a comparable signal-to-noise ratio. Moreover, DAS images can be improved by using a seismic source that has sufficiently large energy within the frequency range matching the spatial resolution of DAS. The temporal resolution of the DAS images can be improved by minimizing the crossline offset between seismic sources and the DAS cable. The seismic images from DAS can be used to support geohazard analysis and various subsurface exploration activities.

scholarly journals Urban Near-surface Seismic Monitoring using Distributed Acoustic Sensing

2019 ◽  
Author(s):  
Gang Fang ◽  
Yunyue Li ◽  
Yumin Zhao ◽  
Eileen Martin
Keyword(s):  
Seismic Monitoring ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Distributed Acoustic Sensing

scholarly journals Distributed acoustic sensing as a tool for exploration and monitoring: a proof-of-concept

2021 ◽  
Author(s):  
Nicola Piana Agostinetti ◽  
Alberto Villa ◽  
Gilberto Saccorotti
Keyword(s):  
High Resolution ◽  
Plane Wave ◽  
Geothermal Field ◽  
P Wave ◽  
Apparent Velocity ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Geothermal Activity ◽  
Distributed Acoustic Sensing ◽  
Microseismic Event

Abstract. We use PoroTOMO experimental data to compare the performance of Distributed Acoustic Sensing (DAS) and geophone data in executing standard exploration and monitoring activities. The PoroTOMO experiment consists of two "seismic systems": (a) a 8.6 km long optical fibre cable deployed across the Brady geothermal field and covering an area of 1.5 x 0.5 km with 100 m long segments, and (b) an array of 238 co-located geophones with an average spacing of 60 m. The PoroTOMO experiment recorded continuous seismic data between March 10th and March 25th 2016. During such period, a ML 4.3 regional event occurred in the southwest, about 150 km away from the geothermal field, together with several microseismic local events related to the geothermal activity. The seismic waves generated from such seismic events have been used as input data in this study. For the exploration tasks, we compare the propagation of the ML 4.3 event across the geothermal field in both seismic systems in term of relative time-delay, for a number of configurations and segments. Defined the propagation, we analyse and compare the amplitude and the signal-to-noise ratio (SNR) of the P-wave in the two systems at high resolution. For testing the potential in monitoring local seismicity, we first perform an analysis of the geophone data for locating a microseismic event, based on expert opinion. Then, we a adopt different workflow for the automatic location of the same microseismic event using DAS data. For testing the potential in monitoring distant event, data from the regional earthquake are used for retrieving both the propagation direction and apparent velocity of the wavefield, using a standard plane-wave-fitting approach. Our results indicate that: (1) at a local scale, the seismic P-waves propagation and their characteristics (i.e. SNR and amplitude) along a single cable segment are robustly consistent with recordings from co-located geophones (delay-times δt ∼ 0.3 over 400 m for both seismic systems) ; (2) the interpretation of seismic wave propagation across multiple separated segments is less clear, due to the heavy contamination of scattering sources and local velocity heterogeneities; nonetheless, results from the plane-wave fitting still indicate the possibility for a consistent detection and location of the event; (3) at high-resolution (10 m), large amplitude variations along the fibre cable seem to robustly correlate with near surface geology; (4) automatic monitoring of microseismicity can be performed with DAS recordings with results comparable to manual analysis of geophone recordings (i.e. maximum horizontal error on event location around 70 m for both geophones and DAS data) ; and (5) DAS data pre-conditioning (e.g., temporal sub-sampling and channel-stacking) and dedicated processing techniques are strictly necessary for making any real-time monitoring procedure feasible and trustable.

scholarly journals Distributed Acoustic Sensing Using Dark Fiber for Near-Surface Characterization and Broadband Seismic Event Detection

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jonathan B. Ajo-Franklin ◽  
Shan Dou ◽  
Nathaniel J. Lindsey ◽  
Inder Monga ◽  
Chris Tracy ◽  
...  
Keyword(s):  
Event Detection ◽  
Surface Characterization ◽  
Seismic Event ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Seismic Event Detection ◽  
Distributed Acoustic Sensing

scholarly journals Distributed Acoustic Sensing for Mineral Exploration: Case Study

2018 ◽  
Vol 2018 (1) ◽  
pp. 1-4
Author(s):  
Andrej Bona ◽  
Roman Pevzner
Keyword(s):  
Mineral Exploration ◽  
Acoustic Sensing ◽  
Distributed Acoustic Sensing
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