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

Abstract

Ambient-noise-based seismic monitoring of the near surface often has limited spatiotemporal resolutions because dense seismic arrays are rarely sufficiently affordable for such applications. In recent years, however, distributed acoustic sensing (DAS) techniques have emerged to transform telecommunication fiber-optic cables into dense seismic arrays that are cost effective. With DAS enabling both high sensor counts (“large N”) and long-term operations (“large T”), time-lapse imaging of shear-wave velocity (V S) structures is now possible by combining ambient noise interferometry and multichannel analysis of surface waves (MASW). Here we report the first end-to-end study of time-lapse V S imaging that uses traffic noise continuously recorded on linear DAS arrays over a three-week period. Our results illustrate that for the top 20 meters the V S models that is well constrained by the data, we obtain time-lapse repeatability of about 2% in the model domain—a threshold that is low enough for observing subtle near-surface changes such as water content variations and permafrost alteration. This study demonstrates the efficacy of near-surface seismic monitoring using DAS-recorded ambient noise.

On the Broadband Instrument Response of Fiber‐Optic DAS Arrays

“…Several authors have observed local noise in DAS data, which we classify here. One type of noise, referred to as common‐mode noise (Ajo‐Franklin et al, ; Bakku, ; Dou et al, ) is characterized by an infinite‐velocity signal (arrives at all channels simultaneously). This is caused by local seismic disturbance near the interrogator, which vibrates the optoelectronic system and leads to an overprinted signal on all channel recordings at the same time.…”

“…Generally, DAS studies have focused on seismic wave phase information, which is sufficient to model seismic wavefield velocities, for example, in vertical seismic profiling (Daley et al, ; Mateeva et al, ), ambient noise velocity inversions (Ajo‐Franklin et al, ; Dou et al, ; Zeng et al, ), and earthquake phase identification (Ajo‐Franklin et al, ; Jousset et al, ; Lindsey et al, ; Yu et al, ). However, true ground motion amplitudes are necessary for many other seismological processing tasks, including full‐waveform inversion, AVO analysis, moment tensor inversion, and attenuation analysis, which the DAS community will likely investigate in the near future (Cole et al, ; Paitz et al, ).…”

The Potential of DAS in Teleseismic Studies: Insights From the Goldstone Experiment

“…In the PoroTomo experiment in Nevada, Wang et al (2018) also found coherent earthquake waveforms recorded at a dense DAS array and a dense geophone array from a local M L 4.3 event. Dou et al (2017) used traffic noise interferometry for seismic monitoring of the near-surface structure. Jousset et al (2018) demonstrated the possibility of using DAS data for subsurface fault zone imaging.…”

“…Zeng et al (2017) extracted noise cross-correlation functions from a DAS array at Garner Valley, California. Dou et al (2017) used traffic noise interferometry for seismic monitoring of the near-surface structure.…”

Vertically Distributed Sensing of Deformation Using Fiber Optic Sensing

“…DFOS with Raman scattering has already been known as distributed temperature sensing and utilized for a host of hydrological and geothermal applications (Briggs et al, 2012;Carlino et al, 2016;Curtis & Kyle, 2011;Selker et al, 2006). Recently, by exploiting changes in Brillouin and Rayleigh scattering induced by external strains, the DFOS technology has been utilized for geohazard sensing including earthquake observations (Dou et al, 2017;Jousset et al, 2018;Lindsey et al, 2017) and landslide detection (Huntley et al, 2014;Lienhart, 2015;Michlmayr et al, 2017;Picarelli et al, 2015;Schenato et al, 2017). While a few studies have explored the feasibility of DFOS for subsidence and strata deformation sensing (Murai et al, 2013;Wu et al, 2015), the understanding of data collected from borehole-embedded FO cables has remained elusive and hence precluded its use in many contexts.…”