This session focuses on the opportunities and challenges of applying fibre-optic sensing in extreme and unconventional environments, including the ocean and volcanic settings, deep boreholes, controlled temperature and pressure laboratory experiments, chemically reactive conditions and extraterrestrial or planetary exploration contexts. We invite contributions that explore novel deployments, experimental designs, and methodological advances enabling fibre-optic measurements where traditional sensors are impractical, as well as innovations that push fibre sensing technology into previously unattainable extreme settings.
By bringing together numerical simulations, laboratory and analogue experiments and field deployments, this session aims to highlight recent breakthroughs, discuss remaining challenges, and identify future directions for fibre-optic sensing, from controlled laboratory experiments to the deepest oceans and beyond Earth.
Distributed acoustic sensing (DAS) has been a research topic for several decades, and in conjunction with the steadily increasing number of various practical applications the interest for this relatively new technology has increased significantly in the past years. There has been a number of significant developments on the hardware side making it possible to interrogate large distance using a fibre cable. Today it is feasible to interrogate between 100 to 200 km, and recent experiments indicate that this can be extended to several thousands km.
During the past decade, we have tested various geophysical applications of fibre optic sensing. In this paper we will show offshore examples including whale tracking, detection of ships and distant storms and other oceanographic examples such as ocean gravity waves, as well as earthquakes. Onshore examples include road traffic, eigenfrequencies of bridges and development of warning systems for rockfall and avalanches. In Norway most railways are equipped with fibre optic cables close to the railway and often deployed in specific pipes 1-2 m away from the line. This causes variation in coupling along the line and we will discuss how these variations can be determined and accounted for in processing. The major challenge for warning systems is to reduce the number of false positive events, and this will be addressed in the talk.
Recently we have demonstrated that it is possible to use fibre optic cables trenched at the seabed to detect silent whales. Using DAS-data containing ultra-low frequencies we show that it is possible to detect the water movements of a whale if it swims closer than approximately 40 m from the fibre. For ships the corresponding distances are typically 400-500 m. Since a fibre optic cable has a long antenna, the fibre can detect low frequency signals that are very hard to measure by a single hydrophone. The huge advantage of the seabed fibre cable is of course the capacity of monitoring large distances (100 km or more), which makes the DAS-technology very attractive for a multifold of applications.
In the future we expect that both the range and signal to noise ratio of DAS-data will increase significantly. In parallel with these huge technical achievements the need for secure handling of data will increase, leaving challenges to the research community that it is important to address and handle.
How to cite: Landrø, M. and Rørstadbotnen, R.: Onshore and offshore fibre optic sensing – examples and lessons learned , Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-124, https://doi.org/10.5194/egusphere-gc14-fibreoptic-124, 2026.
Shallow shelf seas (<200 m depth) cover 7% of the ocean’s surface, yet generate 15-20% of global primary productivity and are vital for fisheries, tourism, and coastal economies. However, the sparsity of sub-surface and seafloor observations makes them under monitored, leaving key circulation processes (e.g.- marine heatwaves) poorly constrained. The MOST project aims to bridge this data gap using distributed fiber optic sensing on submarine cables to perform real-time monitoring of water temperature changes, currents and pressure at the seafloor. The first pilot study area is a commercial network of telecom cables in Guadeloupe where an intermittent three-year time series using BOTDR (Brillouin Optical Time Domain Reflectometry) correlates with the Sea Surface Temperature to within 0.1°C and continuous BOTDR monitoring has begun. Building upon this we will perform continuous DAS (Distributed Acoustic Sensing) and deploy in-situ seafloor instruments. The second study area is the macrotidal Bay of Brest, where a prototype hybrid telecom cable (featuring loose and tight sensor fibers) has been deployed enabling a novel method for separating temperature and mechanical strain signals, with potential application to future telecom cables. In both study areas, fiber sensing observations will be cross-validated by oceanographic and seismological instruments deployed next to the cable to calibrate the signals and upscale our technique to other cables worldwide. Starting with commercial cables on the Brittany shelf, we plan to perform L-band DAS interrogation to avoid disrupting internet data transmission. Leveraging the world’s 1.5 million km of submarine cables, MOST can transform the coastal portions into dense arrays of environmental sensors at unprecedented spatial (<10 m) and temporal (<1 hr) scales to better evaluate and anticipate the impact of climate change on the oceans and the seafloor.
How to cite: Gutscher, M.-A., Quetel, L., Autret, E., Lebrun, J.-F., Philippon, M., Nativelle, C., Vitalis-Simon, S., Le Pape, F., Träsch, M., Repecaud, M., and Lanticq, V.: The MOST project: Monitoring Ocean Seafloor Temperature and currents using fiber optic sensing in shallow shelf seas, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-3, https://doi.org/10.5194/egusphere-gc14-fibreoptic-3, 2026.
The SAFAtor project (SMART cables And Fibre-optic sensing Amphibious demonstrator) was kicked-off in March 2025, as a €30 million infrastructure initiative by the German Helmholtz Association. We investigate critical observational gaps from the continental landmass to the shelf and slope (coordinated by GFZ, and focus of this presentation) and in the deep ocean using novel cable technologies (coordinated by GEOMAR). This infrastructure project further includes the establishment of data services.
Our testbeds comprise sites at onshore and offshore Mount Etna/Italy, from Istanbul into the Marmara Sea/Turkey, and at the Northern Chilean coast. Here, we have started integrating surveying with Distributed Dynamic Strain Sensing (DDSS) into existing Plate Boundary Observatories to address key questions on volcanic processes, fault dynamics, and preparatory phases of earthquakes. Thereby, we want to significantly enhance monitoring capabilities observing tectonic, volcanic, and fluid-driven activities. Further, we tackle technical challenges like amphibious monitoring and recording of strong-motion events for seismic hazard assessment. Using both well proven and also new DAS devices, we will complement this rapidly evolving field also in urban areas. This will allow us to explore near-surface structures and material properties, as well as hydrological processes in connection with hazardous events.
In our presentation we will provide an overview of the overall project concept and address the specific targets of the different tectonic regimes investigated near-coast. We will discuss the experimental setups that we have started implementing in the light of first data gained, helping to optimize hazard research using distributed dynamic strain sensing techniques. Hence, we will contribute ultimately to better prepare areas exposed to hazard at active plate boundaries and volcanic systems in coastal zones.
How to cite: Krawczyk, C., Rodríguez Tribaldos, V., Jousset, P., and Martínez-Garzón, P. and the SAFAtor Team: Near-coast fibre-optic sensing within project SAFAtor, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-101, https://doi.org/10.5194/egusphere-gc14-fibreoptic-101, 2026.
The South Atlantic Ocean and Margin (SAOM) serves as a crucial natural laboratory for studying passive continental margin formation, continental breakup, and the interactions between tectonic, magmatic, and sedimentary processes. This project investigates with DAS and short perido seimographs stations the tectonic evolution and magmatism of SAOM, with particular focus on seaward-dipping reflectors (SDRs), volcanic formations, and the continent-ocean transition zones. The primary objective is to generate high-resolution structural models of SAOM through an integrated approach combining advanced techniques including surface wave tomography, anisotropic analysis, receiver functions, reflected phase analysis, and joint inversion. This innovative methodology will enable precise mapping of subsurface architecture, particularly the crucial crustal transition zone. SDRs, which record volcano-magmatic processes during rifting, will be investigated as key markers to reconstruct the region's magmatic history, including its relationship to crustal thinning, oceanic crust formation, and tectonic activity. This project will examine the role of magmatism in SAOM evolution, analyzing its influence on fault development, fluid migration, and resource accumulation. Spatio-temporal analysis of these processes, from initial rifting through oceanic spreading, will provide new insights into passive margin dynamics. We will present how the project will be carried out and the first steps to be implemented.
How to cite: Franca, G. S. and Chaves, C. A. M. and the PROASA project: Tectonic Evolution and Magmatism of the South Atlantic Ocean and Margin - PROASA project. , Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-89, https://doi.org/10.5194/egusphere-gc14-fibreoptic-89, 2026.
Fiber Optic Sensing and Distributed Acoustic Sensing (DAS) are emerging technologies that are revolutionizing the way we monitor the acoustic and seismic wavefield in the oceans. By turning tens of kilometers of fiber-optic cables into seismo-acoustic sensors with meter-scale spacing, DAS enables unprecedented spatiotemporal monitoring of submarine soundscapes.
GEUS was granted access to four major submarine telecommunication cables with available dark fibers: AURORA between the island of Bornholm and Germany; two segments of Cantat-3, one north of the Faroe Islands and another in the North Sea; and the SHEFA-2 cable between the Faroe Islands and Shetland.
In this presentation, we review various seismo-acoustic signals detected on the four cables, spanning natural and anthropogenic sources. We will dive deeper into the analysis of a submarine explosion in the Baltic Sea to see how a hybrid seismic network comprising DAS and standard seismometer measurements helped characterize the source. We will also present the results of our investigations into the March 10, 2025, M6.5 Jan Mayen earthquake, focusing on its strong T-wave recorded throughout the Greenland and the Norwegian Seas basins.
How to cite: Mordret, A., Rørstadbotnen, R. A., Hjörleifsdóttir, V., Wuestefeld, A., Fønss Jensen, E., Larsen, T., Voss, P., and Dahl-Jensen, T.: T-waves, explosions, and submarine: an overview of the Danish kingdom's seas soundscape, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-91, https://doi.org/10.5194/egusphere-gc14-fibreoptic-91, 2026.
Offshore decommissioning of oil and gas platforms, once fields have completed their productive life, presents several impacts—primarily economic and environmental. However, these impacts can be mitigated, offering both challenges and opportunities (win-win). It is worth noting that offshore platforms, close to the coast, concentrate dense maritime traffic, are prone to environmental, geohazards & subsurface monitoring; not forgetting that they are usually located in strategic areas.
Casablanca platform (offshore Mediterranean, REPSOL operator & CLMV-MOEVE-NATURGY partners) has been operated for more than 40 years until 2021. Located in the continent shelf off Tarragona (Spain), its area is nearby a major Mediterranean port, active fishing grounds, intense surface-wave & storms and presence of a known migration corridor for marine mammals. This infrastructure represents a real opportunity for long-term observations, specifically in an offshore region (> 160 meters water-depth) were natural, anthropogenic, geophysical and biological processes converge periodically.
Last year a submarine fiber-optics cable (Distributed Acoustic Sensing DAS) was deployed in Casablanca platform; with real time data since Q4-2025. This project was carried out under the European Union Next Generation EU in a public-private collaboration between ICM-CSIC, REPSOL, Alcalá University and Aragon Photonics. By transforming submarine optical fiber cable into dense arrays of virtual sensors, this pilot project enables continuous monitoring of physical processes across solid earth, water column not forgetting atmosphere -ocean interface over displayed cable length of seafloor. But this is not just data acquisition, there is a further paramount computing potential ahead. Artificial Intelligence (AI) has been implemented to tailor DAS data to detect and also classify, almost automatically existing signals from several physical domains. In this case after conditioning & denoising it is possible to differentiate seismic events, vessel activity, marine mammals, ocean-wave and infrastructure related noise; among others. Data Analysis supported by artificial intelligence has proved quite useful, at first sight, for continuous offshore monitoring, detection of low magnitude seismic events.
First results, even still provisional, are quite promising and reveal further potential of fiber-optics sensing based on additional cable deployment and focused seafloor design. These real capabilities, not just hypothetical studies, would visualize Casablanca platform as a host scientific observatory for offshore seismicity, ocean noise maritime traffic and possible geohazards, among others. This is a potential step (with real insights) to visualize sustainable & useful future for a legacy asset. A second phase study is already in motion, through a scalable pathway; so, this project just moved from geoscience to real time offshore monitoring. More results to come, stay tuned.
How to cite: Gonzalez-Muñoz, J.-M., Marro, G., Ocampo, G., Toljanic, M., Ugalde, A., Lopez, F., and Ranero, C.: Mediterranean Casablanca-DAS seafloor fibre optics: from geoscience to real time offshore monitoring , Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-26, https://doi.org/10.5194/egusphere-gc14-fibreoptic-26, 2026.
Fibre sensing technology can provide seismic data at a variety of scales, but most studies sensing telecom infrastructure however focus on short (<50 km) cables, due to instrumentation range limitations, presence of line amplifiers and, importantly, difficulty in accessing commercially valuable fibres. This has so far hampered the use of fibre sensing to study low frequency signals—key for global seismic monitoring and deep Earth imaging—for which large inter-channel distances and spatial stacking are required.
In this study, we showcase results from a new project acquiring on- and offshore fibre sensing data on commercial telecom fibres in the North Atlantic Ocean, Irish Sea and across Ireland, using a combination of Distributed Strain Sensing (DSS, also known as DAS) across >400 km on land and near-shore, and new distributed Microwave Frequency Fiber Interferometer (MFFI) technology to sense the 1700 km on the IRIS submarine cable connecting Ireland to Iceland. All data were recorded using technology capable of sensing live, traffic-carrying fibres, and the onshore DSS data were recorded on fibres actively carrying the Irish National Research and Education Network traffic.
Our DSS results show that while having lower signal to noise ratios compared to nearby seismic stations, DSS on noisy telecom fibres can successfully record most Mw>6 teleseismic events worldwide, microseisms originating in the North Atlantic and Irish Sea as well as broadband seismic signal caused by localised rainfall on the cable. In order to sense the North Atlantic Ocean, we present the newly developed MFFI sensor, which uses fibre interferometry in conjunction with high-loss loop backs at line amplifiers, turning each section between amplifiers (50-100 km) of the cable into independent strain sensors. Since its installation in November 2025, we have sensed major teleseismic earthquakes (Mw 7.6 Hokkaido-Japan and Mw 7.4 Molucca Sea-Indonesia), secondary microseisms generated by Atlantic storms and local, ocean-bottom variations in ocean tides.
Our results show that we can leverage the existing telecom infrastructure to perform seismic and environmental sensing over large distances, filling the seismic instrumental gap in the oceans and provide key data for seismic and ocean monitoring and deep Earth imaging.
How to cite: Celli, N. L., Bean, C., Bogris, A., Aias-Karydis, G., Kenny, E., Vergara, R., Jonsson, Ö., and Ruffini, M.: Fibre sensing at regional scales on onshore-offshore telecom cables , Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-31, https://doi.org/10.5194/egusphere-gc14-fibreoptic-31, 2026.
How to cite: Maggi, A., Batista, C., Zigone, D., Le Bris, T., and Barruol, G.: A diagnostic framework for tidal signal recovery under diurnal environmental aliasing: application to a fiber-optic and seismic deployment on Astrolabe Glacier, East Antarctica, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-8, https://doi.org/10.5194/egusphere-gc14-fibreoptic-8, 2026.
In cold climates, rivers are affected by ice cover for several months a year, seasonally transforming hydraulic and hydrological conditions. This, in turn, impacts channel morphology and ecology. During ongoing climate warming, river-ice extent is declining and freeze-up and break-up patterns are changing. River ice break-up in the spring is considered the most dynamic period of the year. It is driven by thermal processes like surface melting in response to rising air temperatures and/or mechanical forces like increased discharge and flow-induced fracturing. However, these processes remain difficult to constrain with observations as field sites are difficult to access and instrument at a sufficient spatial coverage. Here, we present a comprehensive observational dataset combining seismic, Distributed Acoustic Sensing (DAS), and auxiliary measurements that captures the complete river-ice breakup process in a northern river.
We deployed a DAS system along a 400-meter, regulated reach of the Sävar River located at around 64 No latitude in northern Sweden. The fiber-optic cable configuration included a longitudinal section mid-channel on the river ice and a sawtooth pattern across the channel. Additionally, we installed eleven three-component geophones at key cable crossing points to collect benchmark seismograms. During our field campaign between 26 March and 3 April 2025, we captured the complete breakup of the ice cover. Ice failure began on 30 March, and the channel was ice-free on 3 April.
Detections with short-term over long-term averages (STA/LTA) and visual inspection revealed over 2000 ice cracking events. Frequency-wavenumber analysis of the DAS data along the longitudinal cable indicates the presence of the fundamental quasi-symmetric mode (QS0) and the quasi-Scholte (QS) mode. We further discuss event location and waveform modelling to advance the characterization of crack event frequency and orientation (longitudinal vs. cross-channel). Our measurements allow us to asses the roles of environmental factors, particularly river discharge and temperature, in the breakup process. By resolving fine-scale ice fracturing processes, our results provide new constraints on the timing of river-ice breakup and the corresponding ice thickness evolution, with implications for flood hazard assessment, sediment transport, and river management in cold regions under a warming climate.
How to cite: Kang, J., Walter, F., Laporte, S., Polvi, L., Blumenschein, F., Mason, R., and Turowski, J.: When River Ice Breaks Faster Than Expected: One Week of Distributed Acoustic Sensing on the Sävar River in Sweden, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-25, https://doi.org/10.5194/egusphere-gc14-fibreoptic-25, 2026.
Deformation and seismicity often precede and accompany volcanic eruptions. Models of magma emplacement and ground deformation associated with eruptions are obtained from GNSS and InSAR observations and associated seismic source mechanisms from seismometer observations. While satellite sensing techniques benefit from large spatial coverage with coarse temporal resolution and accuracy (mm range), seismometer networks acquire dense temporal data but are sparsely distributed and suffer from spatial aliasing. However, dynamic models of sources prior to the eruptive event are challenging to obtain, because they are in most cases too small or too slow to be observed accurately with conventional instrumentation. Here, we demonstrate that distributed fibre optic sensing with phase optical time domain reflectometry (Φ-OTDR) allows us to retrieve dynamic and static deformation processes associated to magma transfer from the reservoir below Svartsengi in SW Iceland, at depth and through diking events, prior to volcanic eruptions. Since November 2023, we are continuously monitoring an existing telecom fibre optic cable with a commercial iDAS interrogator, set-up on the western Reykjanes Peninsula. Reykjanes Peninsula is the onshore expression of the Mid-Atlantic oceanic ridge, where a series of magmatic intrusions and eruptions have occurred since 2020. Unlike previous studies, the used cable spans across locations from a large inflation/deflation area near dyke outbreaks at its eastern end, to a remote area where little signatures from eruptions are observed at its western end. In-situ down-sampled strain-rate data (1000 Hz to 200 Hz) are transferred continuously via internet to our computing centre at the GFZ in Germany. We further down-sample data to 2 minutes and perform time integration in order to analyse long period strain signals both spatially and temporally. We present resulting distributed dynamic strain (i.e., strain rate) observations and their source inversions associated with a series of eruptions and intrusions. Our inversions comprise a Mogi source and an Okada model, and we test several inversion methods. For each recorded eruption, we invert the distributed spatial strain taken every 2 minutes, allowing us to follow magma progression prior to each eruption with time. We investigate sizes and locations of the deflating reservoir and dykes with observed eruption locations. We also compare faults reactivated during the successive eruptions with the fibre optic cable records. These results show that distributed fibre optic sensing is capable of simultaneous seismological and geodetic observations in a volcanic context, opening the path for a better understanding and potentially improved real-time monitoring of volcanic processes.
How to cite: Jousset, P., Gudnason, E., Currenti, G., Wollin, C., Holstein, L., Maass, R., Diaz-Meza, S., Hurley, M., Prestifilippo, M., Jacobs, E., Walter, T., Hersir, G. P., Sigurdarson, D., and Krawczyk, C. M.: Sources of dynamic and static deformation associated with eruptive and intrusive events on Reykjanes Peninsula, SW Iceland (2023-2026)., Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-97, https://doi.org/10.5194/egusphere-gc14-fibreoptic-97, 2026.
In 2024 an innovative Distributed Fiber Optic Sensing prototype has been set up to interrogate a fiber optic cable installed in a 190-m deep borehole on the southern Etna flank about 5 km away from the summit crater. We use a full-band distributed strain sensing (FB-DSS) fibre optic method, implemented using a reference-based Rayleigh backscatter correlation approach, in which each acquisition is compared with previously recorded reference data to retrieve distributed strain changes with long-term stability at nanostrain-level.
The local strain response is assessed by comparing the distributed signals against natural and controlled deformation sources. Thanks to the nanostrain level sensitivity, variations induced by Earth tide and environmental parameters, including temperature, precipitation and atmospheric pressure, are clearly visible and in agreement with theoretical expectations.
The strain residuals, achieved after the removal of the Earth tide components, show up deformation related to Etna volcano activity. On the morning of 10th November 2024 Etna experienced a weak lava fountain preceded by a short and small seismic swarm. Despite the tiny deformation induced by the volcano unrest, the FB-DSS prototype was able to discern strain variations on the order of 125 nanostrain over 2 h (0.02 nanostrain/s). The strain variations are in agreement with dilatometer and tilt signals recorded by the permanent high-precision deformation network of Etna. No displacements above the background noise level are observed in the GPS data. The joint analysis and modeling of the deformation dataset from the FB-DSS and permanent network allows to track the eruptive activity, constraints the magmatic processes and estimate source parameters. Our findings demonstrate that the FB-DSS approach concurs in bridging the seismo-geodetic bandgap, while offering important advantages over conventional borehole point sensors.
How to cite: Currenti, G., Jousset, P., Liehr, S., Carleo, L., Pellegrino, D., Pulvirenti, M., Krawczyk, C., and Bonaccorso, A.: Detecting volcano unrest at Etna using borehole distributed fibre optic sensing, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-34, https://doi.org/10.5194/egusphere-gc14-fibreoptic-34, 2026.
At TU Delft, a combined geothermal and high-temperature aquifer thermal energy storage (HT-ATES) infrastructure is being developed, linking a deep geothermal doublet to a shallow storage system that buffers the seasonal mismatch between heat supply and demand. Geothermal heat production and seasonal thermal energy storage both require reliable subsurface monitoring to assess reservoir behaviour, system efficiency, and the evolution of injected heat in both space and time.
The site includes injector-producer wells, deep and shallow monitoring boreholes, and a planned set of five storage wells arranged in hot and warm groups for direct use and reheating, respectively. These boreholes are instrumented with fibre-optic systems for distributed strain, temperature, and acoustic sensing, providing an experimental setup for evaluating the role of distributed acoustic sensing (DAS) in geothermal monitoring.
In this study, we present an overview of baseline DAS measurements acquired to support future monitoring of the geothermal site operation. The dataset includes observations from fibre installations deployed inside and outside the casing and enables an initial comparison of acquisition parameters, including pulse width, gauge length, and fibre type. Baseline active-source measurements were acquired using an electric vibrator operating over a 2–180 Hz sweep band, with repeated sweeps to improve signal-to-noise ratio through stacking.
The analysis aims to identify acquisition configurations that provide robust repeatability and sufficient sensitivity for active-source time-lapse monitoring. The work forms the foundation for repeated seismic surveys to target thermal-plume evolution and reservoir response during future operation of the TU Delft system. In the long term, these baseline observations will support the development of 4D full-waveform inversion to track changes in elastic properties resulting from temperature and fluid injection, with the broader goal of improving monitoring and maintenance of geothermal energy systems.
Acknowledgements: This work was supported by the European Union under the Horizon Europe PUSH-IT project (grant no. 1011096566) and by CETP Q-Fibre (proposal code Cetp-FP-2023-00079). CETP Q-Fibre is co-funded by the European Commission (GA no. 101069750), the Netherlands Enterprise Agency (RVO), the Research Council of Norway (RCN), and the U.S. Department of Energy (DOE).
How to cite: Wilczynski, Z., Drijkoningen, G., Dominguez Bureos, M., and Barnhoorn, A.: Baseline DAS observations for active-source time-lapse monitoring at the TU Delft geothermal site, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-57, https://doi.org/10.5194/egusphere-gc14-fibreoptic-57, 2026.
In autumn 2019, fiber-optic cables with both single-mode and multi-mode fibers were permanently installed in an urban multi-well project in Munich, southern Germany, which was under construction at the time. One cable was cemented in place behind the casing to a depth of 700 meters, a practice commonly seen in the oil and gas industry but rare in geothermal energy. Meanwhile, a second cable was permanently suspended in a deviated, 3.7 km long (measured depth) and 2.9 km deep (true vertical depth) production well within the thermal water stream to bottom end. The newly installation was specifically designed and optimized for this purpose. Since then, DTS data, as well as pressure/temperature data from a Fabry-Pérot PT gauge spliced into the cable, have been continuously measured during shut-in, testing, and production phases of the well. DDSS/DAS data were also collected as part of various campaigns, including water injection tests and vertical seismic profiling. In 2023, a third well at the site, an injection well with up to 69° deviation with a more challenging geometry (no production casing in the reservoir “open hole” and large outbreaks), was reequipped with an additional cable including two Fabry-Pérot gauges and integrated into the underground monitoring infrastructure.
This contribution presents key learnings from seven years of continuous fiber-optic monitoring across all operational phases of a geothermal site. We discuss installation concepts and their practical trade-offs, including the challenges of data acquisition and interpretation in a complex urban geothermal setting: distinguishing dynamic strain from thermally induced signals, pump and flow signatures, and other operational states remains a central analytical challenge. The long-term performance of the permanently installed cables is evaluated with respect to fiber integrity, signal degradation, and the risks associated with well interventions as pump changes over a seven-year period. We further assess the potential and current limitations of single-mode DTS in our setting. On the application side, we examine which conventional downhole logging operations can be replaced or validated by the permanent monitoring system, and what benefit continuous monitoring provides for reservoir management and operational decision-making. Finally, we provide an outlook on the planned completion of the site's monitoring infrastructure and the scientific and operational objectives we aim to address with the expanded multi-well fiber-optic network.
How to cite: Schölderle, F., Andy, A., Hart, J., Pfrang, D., Haberer, S., and Zosseder, K.: Seven Years of Fiber Optic Monitoring in Highly Deviated Deep Geothermal Wells: Hard-Won Lessons from Deployment to Long-Term Data Integrity, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-74, https://doi.org/10.5194/egusphere-gc14-fibreoptic-74, 2026.
In tectonic active regions, fault creep induced ground motions represent a hazard that may put at risk infrastructures (railroad, highway, bridges etc.), buildings and industrial constructions. Proper monitoring in this context is not only a prerequisite for risk assessment but is also of value to provide insights into the understanding of fault loading process which helps to constrain seismic hazard. Today, monitoring of fault creep is widely done by means of local in-situ (GPS, extensometers) or broad scale remote sensing (INSAR ect.) measurement techniques which lack either in spatial continuity and range or temporal resolution. Given its quasi-continuity at kilometer scale in space and time, Distributed Fiber Optic Sensing (DFOS) monitoring techniques may represent a promising complementary tool in this respect. Here we provide insights on the monitoring potential using Distributed Strain Sensing (DSS) from an in-situ fault monitoring experiment in a deep underground mine in Sweden. At the so-called Garpenberg mine, seismicity is associated with long-term occurrences (several months to years) of seismic repeaters and multiplets documenting repetitive fault failure in specific zones. Comparison to in-situ strain measurement shows that this repetitive seismic signature is widely driven by aseismic creep of the rockmass following the excavation of stopes (volumes of ~ 27000 m3). Further investigations confirmed that rockmass readjustment and stress redistribution following excavation is dominated by aseismic creep which itself may (but not always) trigger seismicity. DSS monitoring has been applied together with Distributed Acoustic Sensing (DAS) and other fiber optic technologies in order to monitor the full seismic cycle of certain repeater/multiplet targets. DSS allowed detecting multiple active fault structures and associated creeping sequences either triggered from excavation progress and/or self-triggered from interactive loading processes. In addition, reliable first order approximation of fault slip (displacement) could be derived from the recorded strain using a simplified shear zone geometry model. Next to these promising results, currently, the potential of DSS is further explored in a real fault creep monitoring scenario at an outcropping actively creeping fault structure.
How to cite: Kinscher, J.-L., Chambers, D., Bernard, P., Arnaiz Rodriguez, M., and Satriano, C.: DFOS based fault creep monitoring - insights from an underground mine experiment , Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-46, https://doi.org/10.5194/egusphere-gc14-fibreoptic-46, 2026.
We report a new deployment of a purpose-designed, 13-km long optical fiber in the Sea of Galilee, a freshwater lake within a tectonically active basin along the Dead Sea Fault. The fiber trajectory was designed to cross mapped faults, maximize earthquake detection, location, and focal-mechanism estimation capabilities, and intersect existing monitoring stations. The maximum deployment depth is about 35 m. The ~170 km2 lake is covered by 12 strong-motion monitoring stations, which we use to independently validate our seismological analysis. We will present initial results from earthquake monitoring and ambient noise analysis, as well as lessons learned from an academic fiber deployment operation. We suggest that, given adequate planning, such deployments are feasible for many academic groups and can significantly improve observational capabilities in traditionally unmonitored areas.
How to cite: Lellouch, A. and Stein, S.: A 13-km subsea fiber deployment in the Sea of Galilee for earthquake monitoring and subsurface imaging, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-11, https://doi.org/10.5194/egusphere-gc14-fibreoptic-11, 2026.
How to cite: Lozovyi, S.: Distributed fibre-optic strain sensing on cylindrical geomaterial specimens under triaxial stress, pore pressure, and temperature conditions, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-82, https://doi.org/10.5194/egusphere-gc14-fibreoptic-82, 2026.
Trees play a key role in climate-change mitigation and biodiversity conservation, but increasing drought and heat stress threaten their vitality. Monitoring tree water status and stem dynamics is therefore essential, particularly for early stress detection. However, conventional dendrometric approaches are often invasive or lack the spatial and temporal resolution required to resolve fine-scale structural and hydraulic dynamics along stems and branches.
Here, we evaluate Distributed Fibre Optic Sensing (DFOS) as a non-invasive method for continuous, high-resolution dendrometry and strain monitoring in trees. Using a LUNA ODiSI 7100 interrogator based on Rayleigh backscattering, we measure relative microstrain at a gage pitch (spacing of
adjacent gage centre points) of 0.65 mm under laboratory conditions. We test the hypothesis that water transport induces small but measurable changes in stem and branch geometry, producing strain signals that can be used to infer hydraulic and mechanical responses.
Initial experiments were conducted on hazel branch cuttings submerged in water and on a small beech tree under controlled conditions representative of active water transport. These tests provide a proof of concept for assessing signal sensitivity, stability, and the effective spatial resolution achievable in practice. The results are used to identify which strain patterns can be robustly recovered and to evaluate the suitability of DFOS for monitoring dynamic stem responses at scales not accessible with conventional point-based techniques.
We aim to establish the methodological basis for a field-deployable DFOS framework for tree monitoring. Beyond demonstrating feasibility, the approach offers potential for linking fine-scale stem mechanics with tree water transport and stress responses. In the longer term, DFOS could contribute to improved monitoring of tree functioning and resilience under increasingly frequent climate extremes.
How to cite: Schmelzbach, C., Macrae, L., Madonna, C., Di Bella Meusburger, K., and Zweifel, R.: Distributed Fibre Optic Sensing for Tree Dendrometry, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-32, https://doi.org/10.5194/egusphere-gc14-fibreoptic-32, 2026.
Distributed Acoustic Sensing (DAS) offers unprecedented spatial resolution relative to conventional seismic networks. This provides new opportunities to investigate the composition of the recorded seismic wavefield in volcanic environments, which are often highly heterogeneous. At Mt Etna, recent work (Yates et al. 2026) has highlighted the presence of stable spectral peaks that emerge during broadband volcanic tremor. Using seismic stations from the permanent monitoring network, these were found to vary significantly between stations and to respond to seismic velocity changes through proportional frequency shifts. Combined, these observations support the interpretation that they originate from persistent scattering structures that cause resonance-like effects in heterogeneous environments.
In this study, we present a preliminary analysis of DAS data acquired between Zafferana and Linera on the eastern flank of Mt Etna in 2019 (~15 km length). Anthropogenic noise is found to dominate the recorded wavefield during a significant proportion of the day. However, stable spectral peaks are clearly visible during periods of reduced activity (late evening / early morning). We quantify the spatial variability of these peaks, taking advantage of the high spatial resolution offered by DAS. Our work provides the opportunity to (1) better constrain the relative roles of source, path, and site effects in generating stable spectral peaks, and (2) assess subsurface heterogeneity through quantification of the characteristic length scales over which spectral peaks vary. Together, this approach demonstrates the potential of DAS to provide insights into the subsurface at spatial scales not resolvable with conventional seismic networks.
This work has been performed in the frame of USCV-DAS, a Transnational Access to the Eastern Sicily testbed supported by the EU project Geo-INQUIRE. Geo-INQUIRE is funded by the European Commission under project number 101058518 within the HORIZON-INFRA-2021-SERV-01 call.
References
Yates, A. S., Heuninck, S., Barajas, A., Bektas, H., Caudron, C., De Angelis, S., & Zuccarello, L. (2026). Tracking subsurface changes via frequency shifts in volcanic tremor spectral lines: observations from Mt Etna. Geophysical Research Letters, 53(2), e2025GL117819.
How to cite: Yates, A., Jousset, P., Currenti, G., Sens-Schönfelder, C., and Caudron, C.: Probing subsurface heterogeneity through the spatial variability of spectral peaks in DAS data at Mount Etna, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-52, https://doi.org/10.5194/egusphere-gc14-fibreoptic-52, 2026.
Approximately 70% of the Earth's surface is covered by the oceans. Installing permanent seismic sensors on the seafloor is both difficult and costly, resulting in a gap in the the global seismic monitoring. Recently, the potential of using the existing network of submarine fiber-optic cables for the observation of seismic waves has been investigated, several works demonstrating the feasibility of using trans-oceanic subsea cables as seismic sensors (f.ex. Marra 2018,2022; Zhan, 2021; Mazur 2024). In this work, we use a distributed fiber optic sensing (DFOS) prototype capable of measuring the integrated strain between each repeater along the entire length of a fiber optic cable (the repeaters are typically placed 100 km from each other). This instrument is used on the IRIS telecommunication cable, an operational subsea cable connecting Iceland to Ireland, transforming 17 spans of the cable into an array of 17 individual seismic sensors. Signals from several large earthquakes can be observed on the recorded data from the cable and surface waves as well as multiple seismic body wave phases can be tracked across the spans.
To assess the capability of the monitoring system to detect the P-wave phase, we use an STA-LTA algorithm to automatically detect the arrival of P-waves in the data and we compare the phase detections to those predicted by travel-time curves from a catalogue of major earthquakes from the USGS database (with a magnitude above 6 and a distance of 30 to 100° from the fiber-optic subsea cable). We manage to retrieve 40% of our earthquake catalogue with our detection algorithm. However, a large part of our detections are not pickings of the P-wave phase.
How to cite: Lepère, A., Hjörleifsdóttir, V., Gunnarsson, A. I., Mazur, M., Kamalov, V., Karrenbach, M., Williams, E. F., Jónsson, Ö., Fontaine, N. K., Ryf, R., Dallachiesa, L., and Neilson, D. T.: Observations of P-wave phase arrivals from major earthquakes with the IRIS fiber-opticsubsea cable connecting Iceland and Ireland, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-86, https://doi.org/10.5194/egusphere-gc14-fibreoptic-86, 2026.
In deep geothermal wells, conventional downhole data is commonly very limited, especially during long-term plant operation. Since 2021, permanently installed fibre optic cables in one production and one injection well at a hydrogeothermal site in Munich have enabled continuous DTS (Distributed Temperature Sensing) measurements along the entire borehole length (~4 km) as well as pressure monitoring at reservoir depth at 3000 m MD (measured depth) using Fabry–Pérot gauges. In addition, several DDSS (Distributed Dynamic Strain Sensing) campaigns were conducted during different operational stages of the geothermal plant. In this contribution, we present borehole and reservoir processes derived from this unique long-term fibre optic dataset and discuss their implications for reservoir characterization and geothermal field development.
Different approaches were applied to resolve production and injection zones within the reservoir at high spatial resolution. These include energy and mass balance modelling of temperature profiles during production, thermal slug tracking to derive fluid velocities and flow contributions, and analysis of borehole warmback during shut-in periods. DTS-derived results provide rapid and robust characterization of flow zones and extend beyond the spatial and temporal limitations of conventional flowmeter logging. In addition, low-frequency DDSS (LF-DDSS) measurements reveal highly detailed flow dynamics and previously unresolved flow processes within the wells and reservoir. In the injection well, 78 % of the injection happens in the upper 120 m MD of the 1000 m long reservoir section. In the lower half, free convection cells dominate in the wellbore during steady injection and a 40 m thick localized hydraulic anomaly even shows 1 l/s of inflow into the wellbore from the formation.
Furthermore, the temporal evolution of the production/injection temperature and flow zones indicates dynamic changes in reservoir properties during plant operation. Pressure data from fibre optic gauges enables repeated pressure transient analysis (PTA) of shut-in phases. These show that long-term operation has significantly increased the transmissivity of one of the wells and suggest an altered flow regime. The measurements further provide an important basis for calibration and validation of 3D thermo-hydraulic numerical models of the entire six-well system at the Munich plant.
Overall, the presented results show how the applied methodical approaches can improve the geological and reservoir understanding of deep geothermal systems in the Bavarian Molasse Basin and will support future reservoir engineering, field development, and forecasting of long-term well performance.
How to cite: Andy, A., Hart, J., Schölderle, F., Krawczyk, C. M., and Zosseder, K.: Beyond Conventional Monitoring: Permanent Fibre Optic Sensing in a Geothermal Reservoir During Production and Injection, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-100, https://doi.org/10.5194/egusphere-gc14-fibreoptic-100, 2026.
Distributed fibre optic sensing (DFOS) is increasingly used for subsurface monitoring due to its ability to provide dense spatial coverage and a broad range of strain measurements, from slow quasi-static deformation to rapid dynamic signals. Distributed strain sensing (DSS) provides detailed measurements of strain evolution along the fibre, enabling identification of strain localisation. However, linking these measurements to underlying fracturing and failure processes remains challenging, as it is unclear how strain localisation, acoustic emission (AE) activity, and observed fracture development relate to the same underlying fracture process. These signals are often analysed separately, limiting the ability to consistently relate DFOS observations to fracture processes and to understand how these relationships evolve across spatial scales.
In this study we present results from the first stage of a multi-scale experimental campaign designed to investigate how fracture processes are expressed in DSS, AE, and high-speed imaging within a single controlled experiment. The focus is on controlled laboratory experiments on cylindrical sandstone samples of approximately 6 cm in diameter and 12 cm in height. Cyclic loading is used as a controlled probe of damage evolution, allowing progressive activation and reactivation of deformation and fracturing processes over repeated loading cycles. The loading protocol is based on monotonic failure tests and consists of stepwise increases in displacement amplitude with repeated loading–unloading cycles at each level.
High-resolution DSS measurements are conducted on the sample surface to capture the development of strain localisation. In addition, experiments include configurations with fibres deployed both on the sample surface and within a borehole drilled through the sample, enabling direct comparison between externally observed deformation and internal strain response. These measurements are complemented by AE monitoring using sensors located on the sample surface to track microcracking activity and by high-speed camera imaging to observe fracture initiation and propagation. The cyclic protocol enables identification of the onset and evolution of localised deformation, as well as changes in signal response between successive loading cycles. The experiments focus on how the different measurement techniques respond to the same evolving damage state and how signals recorded at the surface relate to those observed within the sample.
Preliminary results show how DSS and AE signals evolve in time and space during fracture nucleation and propagation, and how these relate to directly observed fracture development. The comparison between surface and borehole measurements provides insight into how internal deformation processes are expressed in fibre optic signals, with implications for interpreting borehole-based monitoring data. These observations provide a basis for identifying robust indicators of fracture evolution and assessing their sensitivity to loading history.
This centimetre-scale study forms the foundation for subsequent experiments at larger scales, where similar protocols will be applied to investigate the consistency of observed relationships under more complex conditions. With our multi-scale approach, we aim to improve the interpretation of distributed fibre optic measurements and support the development of more reliable, physics-based monitoring strategies for subsurface systems.
How to cite: Martuganova, E. and Niemeijer, A.: Fibre optic sensing of fracture processes: from small-scale laboratory experiments to multi-scale applications, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-39, https://doi.org/10.5194/egusphere-gc14-fibreoptic-39, 2026.
Well-based Fiber Optic Cable (FOC) constitutes a novel technology for sensing and monitoring, with high spatial resolution, strain resulting from changes in reservoir pressure due to thermal, mechanical, and hydraulic stresses triggered by critical activities which endanger wellbore stability.
As wellbore integrity assessments depend on reliable, calibrated strain measurements, the strain recorded in such configurations needs to be corrected for coupled stresses across multiple media, such as cement-formation systems.
In this research, we aim to enhance the understanding of mechanical stress transfer in cement-rock formation systems through laboratory experiments by recording and comparing FOC strain measurements with 2-D strain-gage measurements.
We crafted two cylindrical sandstone samples of 50 mm diameter and 100 mm height with a concentric hole where concrete of standard mix was poured; one of the samples is equipped with a segment of fiber-optic cable coiled at the concrete-rock interface, and a second segment coiled around the external surface of the rock sample. The second sample is equipped with a set of 2D strain gauges: three are placed at the concrete-rock interface, and three more on the external surface of the sandstone.
Both samples are subjected to the same stress protocol: cyclic uniaxial compression with increments at the end of each cycle over the entire elastic regime until yielding.
The end goal is to provide FOC data calibration for formation-cement interface under uniaxial mechanical stress, as well as providing insights into the micromechanical behavior of the formation-cement interaction.
This work was supported by CETP Q-Fibre (proposal code Cetp-FP-2023-00079). CETP Q-Fibre is co-funded by the European Commission (GA no. 101069750), the Netherlands Enterprise Agency (RVO), the Research Council of Norway (RCN), and the U.S. Department of Energy (DOE).
How to cite: Dominguez-Bureos, M., Wilczynski, Z., and Barnhoorn, A.: Stress-transfer characterization in a concrete-rock system using DSS measurements, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-56, https://doi.org/10.5194/egusphere-gc14-fibreoptic-56, 2026.
Distributed Acoustic Sensing (DAS) has emerged as a powerful fibre-optic technology for high-resolution seismic monitoring, particularly in environments where conventional sensor deployment is limited or impractical. Its ability to transform standard fibre-optic cables into dense arrays of virtual sensors offers significant advantages for applications in extreme and remote settings, including planetary exploration. In this study, we investigate the feasibility and performance of DAS for subsurface characterization under controlled lunar-analogue conditions.
The experiment was conducted in the LUNA Moon analog test facility at the German Aerospace Center (DLR), which provides a controlled environment designed to simulate key aspects of extraterrestrial surfaces. The primary objective was to evaluate the applicability of refraction seismics for detecting subsurface structures analogous to water ice deposits, which is one of the most critical resources for future lunar and planetary missions.
A DAS system was deployed along a fibre-optic cable to record seismic wavefields with high spatial resolution. To generate seismic energy, we employed a combination of active source types with complementary characteristics. Impulsive sources, such as sledgehammer impacts, were used to produce high-amplitude, broadband signals suitable for shallow subsurface imaging. In addition, a PASS (Portable Active Seismic Source) system was utilized to provide a controlled source sweep with distinct frequency features, enabling a systematic coverage of the frequency spectrum and the corresponding penetration depths.
The integration of these source types allows for enhanced flexibility in seismic data acquisition and facilitates a more comprehensive analysis of subsurface properties. The recorded DAS data were processed using refraction seismic techniques to identify velocity contrasts associated with potential ice-equivalent layers. The controlled test environment enables direct assessment of signal quality, repeatability, and resolution, offering valuable insights into the strengths and limitations of DAS under conditions relevant to planetary exploration.
Our results demonstrate that DAS is capable of capturing seismic signals in a lunar-analogue setting and shows high sensitivity to heterogenities in the shallow subsurface. The combination of different seismic sources proves particularly effective in optimizing data quality across varying depths and frequency ranges. These findings highlight the potential of fibre-optic sensing technologies as a robust and scalable solution for future geophysical investigations beyond Earth. This work contributes to the advancement of seismic exploration methodologies for extreme environments and supports the development of innovative sensing strategies for upcoming missions targeting the Moon and other planetary bodies.
How to cite: Schoeder, N., Zeckra, M., and Knapmeyer-Endrun, B.: Distributed Acoustic Sensing for Subsurface Characterization in a LUNA Moon analog test facility, Galileo conference: Fibre Optic Sensing in Geosciences, Aussois, France, 31 Aug–4 Sep 2026, GC14-FibreOptic-10, https://doi.org/10.5194/egusphere-gc14-fibreoptic-10, 2026.
