Sensing Earth and environment dynamics by telecommunication fiber-optic sensors: an urban experiment in Pennsylvania, USA

Abstract

Abstract. Continuous seismic monitoring of the Earth's near surface (top 100 m), especially with improved resolution and extent of data both in space and time, would yield more accurate insights about the effect of extreme-weather events (e.g., flooding or drought) and climate change on the Earth's surface and subsurface systems. However, continuous long-term seismic monitoring, especially in urban areas, remains challenging. We describe the Fiber Optic foR Environmental SEnsEing (FORESEE) project in Pennsylvania, USA, the first continuous-monitoring distributed acoustic sensing (DAS) fiber array in the eastern USA. This array is made up of nearly 5 km of pre-existing dark telecommunication fiber underneath the Pennsylvania State University campus. A major thrust of this experiment is the study of urban geohazard and hydrological systems through near-surface seismic monitoring. Here we detail the FORESEE experiment deployment and instrument calibration, and describe multiple observations of seismic sources in the first year. We calibrate the array by comparison to earthquake data from a nearby seismometer and to active-source geophone data. We observed a wide variety of seismic signatures in our DAS recordings: natural events (earthquakes and thunderstorms) and anthropogenic events (mining blasts, vehicles, music concerts and walking steps). Preliminary analysis of these signals suggests DAS has the capability to sense broadband vibrations and discriminate between seismic signatures of different quakes and anthropogenic sources. With the success of collecting 1 year of continuous DAS recordings, we conclude that DAS along with telecommunication fiber will potentially serve the purpose of continuous near-surface seismic monitoring in populated areas.

Evaluating seismic beamforming capabilities of distributed acoustic sensing arrays

“…Dense seismometer arrays play a central role in understanding various geological phenomena, including earthquake rupture behaviour (Kiser and Ishii, 2017;Meng et al, 2011), micro-seismicity (Inbal et al, 2016), fault zone structure (Zigone et al, 2019), and deep crustal and mantle geology (Jiang et al, 2018;Lin et al, 2013). Moreover, seismic arrays also serve civil protection purposes through monitoring nuclear test ban treaty violations (Ringdal and Husebye, 1982), monitoring volcano deformation and activity (Inza et al, 2011;Nakamichi et al, 2013), and potentially issuing earthquake early warnings (Meng et al, 2014).…”

The seismic wavefield as seen by Distributed Acoustic Sensing (DAS) arrays: local, regional and teleseismic sources

“…A consequence of differencing is that a single DAS trace can mix aspects of the wavefield with different character, e.g., refracted and reflected segments with similar timing separated by the gauge length. Such an effect was noted by Zhu et al, (2021) in a comparison of a spread geophone and DAS records close to a hammer blow. Near the source some cancellation can occur from differencing.…”

“…Event monitoring has been carried out in a variety of settings including reservoir stimulation (e.g. Karrenbach et al, 2019;Baird et al, 2020;Binder et al, 2020), geothermal seismicity (Li and Zhan, 2018), glacier icequakes (Walter et al, 2020;Hudson et al, 2021) and urban monitoring (Dou et al, 2017;Song et al 2021;Zhu et al, 2021). Earthquake studies have used events at regional ranges Wang et al, 2018;Jousset et al, 2018;Ajo-Franklin et al, 2019;Sladen et al, 2019;van den Ende and Ampuero, 2021) and out to teleseismic distances (Lindsey et al, 2020;Paitz et al, 2020).…”

“…Because the nature and appearance of seismic ground velocity as recorded by seismometers is much more familiar than directional strain, many authors have made efforts to convert DAS strain-rate signals into equivalent ground velocity in different scenarios (e.g., Daley et al, 2016;Egorov et al, 2018;Wang et al, 2018;Zhu et al, 2021). However, the geometries of many cable layouts are not well suited to such conversion, with only short lengths in a consistent direction.…”

Deep Deconvolution for Traffic Analysis with Distributed Acoustic Sensing Data

“…It is likely that fibre-optic sensing will contribute significantly to future developments of smart cities in relation to solid media, including subsurface characterisation [35], infrastructure monitoring of railways [36] and roads [14], and structural integrity evaluations [2]. At a regional scale, fibreoptic sensing has proven useful for recording earthquakes [37] and avalanches [38], monitoring glaciers [39], and inferring hydrological conditions of the subsurface [7]. As extreme weather events like violent storms and droughts will become more likely in the near future [40], dense instrumentation and continuous observations of the subsurface will be useful (or even critical) for agriculture, water, land and forest management, preventive wildfire measures, and slope stability surveillance.…”