Spatiotemporal evaluation of Rayleigh surface wave estimated from roadside dark fiber DAS array and traffic noise

Czarny, Rafał; Zhu, Tieyuan; Shen, Junzhu

doi:10.26443/seismica.v2i2.247

Cited by 3 publications

(1 citation statement)

References 31 publications

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“…J. Spica et al, 2020), mine blast waveforms (Fang et al, 2020;Zeng et al, 2021), shock waves from thunder (Zhu & Stensrud, 2019), and detected T-phases and other acoustic waves (Rivet et al, 2021;Ugalde et al, 2021). Several studies have also illustrated the utility of continuous DAS data in monitoring seasonal changes in the shallow subsurface (Czarny et al, 2023;Rodríguez Tribaldos & Ajo-Franklin, 2021;Yang & Shragge, 2023). Crucial to this study, Viens 2022) recently demonstrated the ability of DAS to characterize the non-linear behavior of offshore sediments during the passing of seismic waves from earthquakes.…”

Section: Introductionmentioning

confidence: 69%

Shallow Soil Response to a Buried Chemical Explosion With Geophones and Distributed Acoustic Sensing

Viens,

Delbridge

2024

JGR Solid Earth

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Shallow sediments can respond non‐linearly to large dynamic strains and undergo a subsequent healing phase as the material gradually recovers following the passing of seismic waves. This study focuses on the physical changes in the subsurface caused by the shaking from a buried chemical explosion detonated in a borehole in Nevada, USA, as a part of the Source Physics Experiment Phase II. The explosion damaged the shallow subsurface and modified the frequency content recorded by 491 geophones and 2240 Distributed Acoustic Sensing (DAS) channels within 2.5 km from surface ground zero. We observe a gradual shift of resonance frequencies in the 10–25 Hz frequency band in the hours following the explosion and develop a method to characterize the related logarithm‐type healing process of the shallow (i.e., upper ∼25 m) subsurface. We find that stronger levels of ground motion increase the relative degree of damage and duration of the subsurface healing; with the spall region exhibiting the largest degree of damage and longest healing recovery time. We observe coherent spatial patterns of damage with the region located to the southeast of the explosion exhibiting more damage than the southwest region. This study demonstrates that both DAS and co‐located geophones capture similar temporal changes associated with the physical processes occurring in the subsurface, with the high‐density sampling of DAS measurements enabling a new capability to monitor the fine‐scale changes of the Earth's shallow subsurface following the detonation of a buried explosion.

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Section: Introductionmentioning

confidence: 69%

Shallow Soil Response to a Buried Chemical Explosion With Geophones and Distributed Acoustic Sensing

Viens,

Delbridge

2024

JGR Solid Earth

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Tidally modulated seismic velocity changes observed using submarine dark fiber and the virtual-source method

Chamarczuk,

Ajo-Franklin,

Sobolevskaia

et al. 2024

GEOPHYSICS

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Natural cyclical stress perturbations, including wet and solid earth tides, coupled to repeatable seismic monitoring approaches, provide a tool for understanding the elastic properties of rocks at depth. Ocean tides in particular perturb the overburden and pore pressure, affecting hydraulic and elastic rock properties. The recent emergence of distributed acoustic sensing (DAS) and seismology utilizing existing dark telecom fiber offers an unprecedented opportunity to instrument the seas and oceans with seismic monitoring networks of large aperture, fine spatial resolution, and broadband sensitivity. We use a submarine dark fiber array to methodologically assess whether changes in seafloor seismic velocities are modulated by ocean tidal loading. Considering oceanic ambient noise in the frequency range between 1 and 5 Hz, we find it possible to retrieve reliable surface-wave estimates using relatively short time windows (∼60 min). Next, utilizing the power of linear arrays to capture ambient noise energy from stationary-phase zones, and ambient noise processing techniques commonly used in DAS applications for subsurface monitoring in urban settings, we introduce a methodological approach to turn each segment of dark fiber into a short-offset monitoring array (2 km), providing redundant, hourly, surface-wave estimates. Using four days of ambient noise data recorded by the Monterey Accelerated Research System (MARS) 20 km section offshore cable, we generate virtual-source gathers for 10 segments spanning the whole MARS cable. We then use virtual-source data from one segment to estimate hourly velocity changes that are then quantitatively compared to tidal data. The results suggest that changes in seafloor seismic velocities are likely modulated by tidal height, even in regions without large tidal excursions. This advance demonstrates a new application of submarine telecom fibers for monitoring the seismic stress response of near-seafloor sediments.

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Passive Seismic Imaging of Urban Environments Using Distributed Acoustic Sensing: A Case Study from Melbourne, Australia

Lai,

Miller,

Jiang

et al. 2024

The Seismic Record

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Distributed acoustic sensing (DAS) offers a cost effective, nonintrusive method for high-resolution near-surface characterization in urban environments where conventional geophysical surveys are limited or nonexistent. However, passive imaging with DAS in urban settings presents challenges such as strong diurnal traffic noise, nonlinear array geometry, and poor fiber coupling to the ground. We repurposed a dark fiber in Melbourne, Australia, into a 25 km DAS array that traces busy arterial roads, tram routes, and orthogonal sections. By employing noise cross correlation and array beamforming, we calculated dispersion curves and successfully inverted for a near-surface shear-wave velocity model down to 100 meters. Stationary seismic sources are maximized by selecting daytime traffic signals, thereby recovering surface waves and reducing interference from acoustic waves from man-made structures in the subsurface. Poorly coupled channels, which are linked to fiber maintenance pits, are identified through cross-correlation amplitudes. The dispersion curve calculation further considers the channel orientation to avoid mixing Rayleigh and Love waves. Using a trans-dimensional Markov chain Monte Carlo sampling approach, we achieved effective model inversion without a prior reference model. The resulting near-surface profile aligns with mapped lithology and reveals previously undocumented lithological variation.

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Spatiotemporal evaluation of Rayleigh surface wave estimated from roadside dark fiber DAS array and traffic noise

Cited by 3 publications

References 31 publications

Shallow Soil Response to a Buried Chemical Explosion With Geophones and Distributed Acoustic Sensing

Shallow Soil Response to a Buried Chemical Explosion With Geophones and Distributed Acoustic Sensing

Tidally modulated seismic velocity changes observed using submarine dark fiber and the virtual-source method

Passive Seismic Imaging of Urban Environments Using Distributed Acoustic Sensing: A Case Study from Melbourne, Australia

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