The first commercially available fibre-optic Distributed Acoustic Sensing (DAS) system, Cobolt, was released in 2004, with early uptake driven by applications in perimeter security, pipeline monitoring, and upstream oil and gas operations. Although these deployments demonstrated the disruptive potential of DAS, it is only within the past five years that the geoscience community has widely embraced the technology, exploiting its ability to deliver continuous, high-fidelity measurements with exceptional spatial and temporal resolution.

Historically, commercially available DAS systems were optimised for industrial monitoring rather than scientific metrology. As a result, key requirements of geoscience applications—such as quantitative accuracy, extreme sensitivity, extended range, and robustness in challenging environments—were not primary design drivers. This situation is now changing rapidly as geoscience applications mature and expand. This contribution reviews the principal performance characteristics that define the suitability of modern DAS systems for geoscience research and examines how recent technological developments are addressing these needs.

Five performance parameters are of particular importance. First, the transition from amplitude-based, qualitative DAS to phase-based, quantitative systems has enabled true strain-rate and strain measurements suitable for metrological applications. Second, instrument sensitivity has improved by several orders of magnitude, with contemporary systems achieving pico-strain-level detection along standard telecom fibre. Third, measurement range—ultimately limited by available backscattered photons in pulsed DAS—has been extended beyond 150 km through the adoption of spread-spectrum interrogation techniques. Fourth, spatial resolution continues to improve, with gauge lengths of ≤1 m and sampling intervals of ≤0.5 m now routinely achievable, and further reductions anticipated. Finally, dynamic range remains a critical consideration for high-amplitude signals such as earthquakes; however, reductions in gauge length provide a clear pathway to mitigating cycle-skipping limitations, supporting the future use of DAS in Earthquake Early Warning (EEW) systems.

Alongside raw performance, the ability to quantify and compare DAS system capabilities has become increasingly important. Industry-led efforts have resulted in well-defined test methodologies and performance metrics, providing a common framework for objective evaluation of DAS instruments used in scientific studies.

Practical deployment considerations are also shaping system design. Reduced size, weight, and power (SWaP) enable operation in remote and hostile environments, while improved reliability, passive cooling, and environmental sealing facilitate long-term field installations. These advances are particularly relevant to emerging marine and subsea applications, where low-power, marinised DAS systems are required for seabed deployment.

Finally, the growing complexity of DAS instrumentation places increasing emphasis on software. Automated configuration, intuitive user interfaces, and integrated edge-processing capabilities are becoming essential to ensure that non-specialist users can reliably extract high-quality scientific data.

Together, these developments signal a transition in DAS from an industrial monitoring tool to a mature geoscience instrument, with continued innovation expected to further expand its role across solid-Earth, cryospheric, and marine research over the coming decade.

How to cite: Hill, D.: DAS design features critical to geoscience applications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4295, https://doi.org/10.5194/egusphere-egu26-4295, 2026.

EGU26-4295

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The aim of this study is to assess the potential of distributed fiber-optic sensors for measuring strain and temperature in order to monitor the structural integrity of underground mining drifts and chambers. The work is conducted within the framework of the project “Model coupling in the context of a virtual underground laboratory and its development process” (MOVIE). The overall MOVIE project aim is intended to support the creation of a digital twin, thereby improving safety and operational efficiency through enhanced digital planning across various mining environments. Time-dependent, spatially distributed temperature and rock deformation data will be recorded along fiber-optic sensing cables. These measurements will serve as boundary conditions for integrated geometrical and geomechanical models of the drift and chambers. In the initial phase, a 60-meter-long drift is instrumented using fiber-optic Brillouin-based Distributed Temperature and Strain Sensing (DTSS). Based on laboratory tests and considering the specific environmental conditions of the subsurface mine, i.e., ambient temperature variations, surface roughness, dust, and humidity, the optimal adhesive bonding materials and technique for direct cable installation on gneiss host rock was identified and successfully implemented. Following the initial monitoring setup, further experimental investigations are planned, including the monitoring of induced deformations in yielding arch support, rock bolts and the rock in contact with a hydraulic prop. The drift geometry and the spatial location of the fiber-optic cables within the drift are given by a 3D point cloud. Therefore, a 3D point cloud was captured after the fiber-optic cable installation using a high-end mobile mapping SLAM platform geo-referenced in a project-based coordinate frame. The locations of the geo-referenced fiber-optic cables will be correlated with the acquired DTSS measurements along the fiber-optic sensing cables. Ultimately, the meshed 3D point cloud will serve as foundational input for the combined geometrical and geomechanical model, forming the basis for a virtual reality-compatible digital twin enriched with real-time sensor data.

How to cite: Martin, M. D., Nöther, N., Farys, E., Facchini, M., and Paffenholz, J.-A.: Distributed Fiber-Optic Sensing for Strain and Temperature Monitoring in an Underground Mine to Enable Digital Twin Integration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7427, https://doi.org/10.5194/egusphere-egu26-7427, 2026.

EGU26-7427

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Fig. 1: Map of the REFIMEVE network (green links) and its connection to European links.

In recent years, significant technological progress has demonstrated the feasibility of using the long distance fiber optic links as large scale distributed networks for environmental sensing [1]. Optical fibers are inherently sensitive to external perturbations: their mechanical structure responds to strain, while the light propagating within them undergoes measurable intensity and phase variation when subjected to vibration or seismic waves. A notable example is the French national research infrastructure REFIMEVE [2], which distributes ultrastable time and frequency references across more than 9000 km of fiber links connecting laboratories throughout France and Europe (see Fig. 1). The infrastructure has demonstrated strong potential for geophysical studies [3]. Applications such as earthquake detection, volcano monitoring, and environmental hazard surveillance are attracting increasing interest worldwide, particularly because they can leverage already existing fiber networks. In this context, the European project SENSEI (Smart European Networks for Sensing the Environment and Internet Quality) [4] aims to harness this potential by developing the next generation photonic technologies for detecting both natural phenomena, such as earthquakes, volcano activity, and anthropogenic events including construction activity or vehicular traffic.

Within this framework, one of our objectives is to develop a coherent optical frequency domain reflectometry (C-OFDR) [5]. Current systems are limited to approximately 100 km by the coherence length of the laser source.  Here, we take benefit from the low frequency noise laser source generated by REFIMEVE frequency reference in order to extend the sensing range. In our setup, the output of a low noise laser is frequency modulated and a fiber under test is studied in a Michelson interferometer configuration. By analyzing the Rayleigh backscattered signal along the fiber, the system enables detailed diagnostics of the fiber under test including the detection of localized fiber deformations, faulty connectors, attenuation variations, and disturbances induced by environmental vibrations. As a first demonstration, we tested a prototype over a long range fiber link made of laboratory spools extending up to 335 km. The system successfully identified the position of the optical amplifier and a PC connector placed at the end of the fiber with km scale spatial resolution. In addition, vibration induced perturbation was observed and is under study, highlighting the potential of this technique for seismic applications. In future work, we plan to deploy the C-OFDR system on the operational REFIMEVE fiber network to evaluate its performance under real field conditions. This approach positions C-OFDR as a powerful tool for telecommunication infrastructure monitoring and distributed geophysical sensing.  

References :

[1] G. Marra et al., Science 361 (2018), https://doi.org/10.1126/science.aat4458

[2] REFIMEVE, https://www.refimeve.fr/en/homepage/

[3] M. B. K. Tønnes, PhD Thesis (2022), https://hal.science/tel-03984045v1

[4] SENSEI, https://senseiproject.eu/

[5] C. Liang et al., IEEE Access. 9 (2021), DOI: 10.1109/ACCESS.2021.3061250

How to cite: Show, D., Dutta, B., Abdelhak, M., Lopez, O., Hilico, A., Amy-Klein, A., Chardonnet, C., Pottie, P.-E., and Cantin, E.: Long range Coherent-Optical Frequency Domain Reflectometry for large scale distributed sensing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13083, https://doi.org/10.5194/egusphere-egu26-13083, 2026.

EGU26-13083

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Distributed Acoustic Sensing (DAS), leveraging existing fiber optic infrastructure, represents a groundbreaking advancement in seismic monitoring. By converting telecommunication cables into dense arrays of virtual sensors, DAS enables continuous spatial coverage and enhanced sensitivity to seismic waves in remote or logistically constrained environments. This capability positions DAS as a complementary or alternative tool to traditional seismic networks, offering cost-effective, low-maintenance solutions for geophysical research and hazard monitoring.

This study focuses on the Premise-2 experiment, conducted at the Low-Noise Underground Laboratory (https://www.lsbb.eu/) in Rustrel, France, a site renowned for its low seismic noise. The experiment integrates active and passive seismic acquisitions, capturing both ambient noise and controlled seismic signals to assess DAS’s ability to detect and characterize events. Multiple fiber optic cable types and installation methods (laid on the ground, with sand bags, buried, or structurally attached) are evaluated to determine their impact on signal sensitivity, spatial resolution, and measurement robustness.

This study provides critical insights into optimal DAS deployment configurations for seismological applications while highlighting the challenges posed by large-scale data acquisition. The research underscores the need for advanced algorithms and specific workflows to fully exploit DAS’s potential. To characterized the events, we have used a workflow using automatic P and S arrival phases. We filtered these arrivals with an associator to select only detections that could be linked to an event. Then we tried different location algorithms to get a complete workflow from the acquisition to the location of the events.

How to cite: Brémaud, V. and Madelaine, C.: Fiber optic cables (DAS) for seismic event detection – An underground case study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13151, https://doi.org/10.5194/egusphere-egu26-13151, 2026.

EGU26-13151

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Optical fiber measurements have been demonstrated to be useful in assessing geophysical near-surface parameters and in detecting seismological events in newly accessible regions (e.g. cities, ocean floor, highways) by leveraging the existing fiber-optic infrastructure. In particular, laser interferometry performed with DAS systems (Distributed Acoustic Sensing) allows measuring the cable axial strain related to passing seismo-acoustic waves, at any point along the fiber and over tens of kilometers of cable.

However, compared to traditional seismic sensors the instrumental response of DAS remains unclear, and there is in particular a critical need to better understand how the measurements are influenced by the nature of the fiber optic cable and its coupling to the ground or medium under study. To explore this question, we present results from two active seismic campaigns carried out in the low-noise  underground tunnel LSBB (Laboratoire Souterrain à Bas Bruit), in southeastern France.

We recorded multiple active sources (TNT detonations and hammer shots) by a 10km and 2km long underground optical fiber set-ups and with conventional seismic sensors as well. We tested along both campaigns different optical fiber cable designs and different types of coupling conditions (sealed, sandbags weighted, freely posed) installed in parallel. This experimental setup provides a unique opportunity to examine in detail and quantify the possible variations in the strain signals recovered from DAS data.

Preliminary observations reveal significant discrepancies in the recorded data depending on the coupling conditions. The characteristics of the deployed source result in a signal that is primarily concentrated in the high-frequency range, for which the sealed fiber does not necessarily exhibit a significantly improved response. Additionally, the acoustic wave generated by the hammer-shot echo, propagating through the air, is strongly amplified in all cables covered by sandbags. We propose that the sandbags increase the interaction area between that signal and the cables, thereby enhancing reverberation.

Furthermore, we observe systematic differences in the maximum amplitudes recorded by the different cables tested, with the telecom cable consistently exhibiting lower amplitudes than other specialized cables, suggesting a lower sensitivity. However, this reduction is relatively modest, and when combined with the substantially lower cost of telecom cables, indicates that they remain a cost-efficient alternative for certain experiments. Additional observations and detailed analyses from this study will be presented.

Keywords: Coupling, fiber optics, DAS measurements, strain rate, active seismic, LSBB.

How to cite: Carrillo-Barra, V., Mercerat, D., Brémaud, V., Sladen, A., Sèbe, O., Vallage, A., and Ampuero, J.-P.: Unveiling type of fiber and coupling conditions effects on geophysical DAS measurements, results from underground experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14230, https://doi.org/10.5194/egusphere-egu26-14230, 2026.

EGU26-14230

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Distributed Acoustic Sensing (DAS) provides dense, meter-scale ground-motion measurements along fiber-optic cables. However, developing ground-motion models (GMMs) from DAS data is challenging because observations are controlled by DAS-specific factors such as cable coupling, orientation, and channel correlation. In this study, we present the first regional, partially non-ergodic DAS-based GMM that explicitly identifies and quantifies cable-related contributions to ground-motion variability. We analyze strain-rate data from a 400-channel DAS array at the Milun campus in Hualien City, Taiwan, compiling peak strain rates and Fourier amplitudes (0.1–10 Hz) from 77 regional earthquakes (3<M<7, 45<R<170 km). Building on classical seismometer-based GMMs, we extend the variability framework to account for (1) cable coupling influenced by installation and environment types, (2) cable orientation, and (3) channel correlation inherent to DAS measurement principles and array geometry. Channel correlation is modeled using Matérn kernels parameterized by along-fiber and spatial proximity distances. The resulting DAS-based GMM shows magnitude-distance scaling comparable to classical models, while decomposing variability into physically interpretable components. Cable coupling emerges as a dominant broadband source of within-event variability, whereas orientation effects capture repeatable, frequency-dependent earthquake source radiation patterns. Modeling channel correlation significantly reduces channel-related standard deviations, demonstrating that treating DAS channels as independent observations biases uncertainty estimates. Overall, our results show that DAS-derived ground motions require a fundamentally different variability framework than that of classical GMMs, highlighting the importance of deployment metadata and correlation modeling. This approach provides a statistical and physical foundation for next-generation seismic hazard assessments using dense fiber-optic sensing.

How to cite: Lin, C.-R., von Specht, S., and Cotton, F.: What Controls Variability in DAS Earthquake Observations? Implications for Ground-Motion Models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4603, https://doi.org/10.5194/egusphere-egu26-4603, 2026.

EGU26-4603

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Applied to existing but underutilized fiber-optic networks (dark fibers), Distributed Acoustic Sensing (DAS) offers an attractive approach for large-scale seismic monitoring with minimal deployment effort. However, the approach introduces specific challenges, as existing infrastructures were not designed for this purpose, leading to constraints related to sensor coupling, heterogeneous installation conditions, and limited characterization of the measurement points. In the frame of the RUBADO project, we investigate the potential and limitations of DAS applied to dark fibers to provide seismic observations supporting both operational monitoring and characterization of deep geothermal reservoirs. The approach is implemented at multiple spatial scales within the Upper Rhine Graben, where several geothermal plants are currently operating, under development, or in the planning phase. In this context, research activities within the project specifically target key practical challenges related to the use of DAS on dark-fibers for the seismic monitoring of geothermal reservoirs.

Currently, data are recorded along a ~20 km fiber-optic line using the KIT infrastructure, which will support the monitoring of the drilling of a 1.4 km-deep geothermal well at KIT Campus North. We present early results from local and regional seismic monitoring and associated methodological approaches for signal enhancement and seismic event detection. We also introduce a framework for subsurface characterization that leverages the frequent vehicle-generated signals observed in the DAS recordings. We then outline planned measurements at the scale of the Upper Rhine Graben, where a key feature is the simultaneous use of multiple dark-fiber lines. Given the geometry of the planned dark-fiber network, DAS observations will enable the simultaneous monitoring of several geothermal sites with favorable spatial coverage.

How to cite: Azzola, J. and Gaucher, E.: Seismic monitoring of geothermal reservoirs using Distributed Acoustic Sensing on dark fibers: the RUBADO project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8212, https://doi.org/10.5194/egusphere-egu26-8212, 2026.

EGU26-8212

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The PITOP geophysical test site, operated by the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) in north-eastern Italy, provides a unique experimental environment for testing seismic acquisition technologies under realistic field conditions. Covering ~22,000 m², PITOP was established to support the development and validation of geophysical methods and instrumentation in both surface and borehole installations. Here, we evaluate PITOP’s potential for Distributed Acoustic Sensing (DAS) experiments, focusing on small-scale seismic measurements relevant to urban settings and engineering applications. 

Five boreholes with distinct purposes and instrumentation are available at the PITOP site, including a water well (PITOP1), two 400-m-deep wells associated with geosteering research (PITOP2 and PITOP3), a 150-m-deep borehole permanently equipped with optical fibre for DAS measurements (PITOP4), and a recently drilled well dedicated to geoelectrical surveys (PITOP5). The site also hosts a surface-deployed fibre-optic cable, containing both linear and helicoidal fibers, and about 20 3C seismic nodes. Finally, several seismic sources are available, which are a borehole Sparker Pulse, suitable for crosshole VSP configurations, and two surface vibratory sources, the IVI MiniVib T-2500, which can generate sweeps in the 10–550 Hz frequency range, and the ElViS VII vibrator, designed for frequencies between 20 and 220 Hz.

We conducted three dedicated experiments:  (i) cross-hole measurements with sources in PITOP3 at depths of 10, 50, 75, and 100 m, and DAS recording in PITOP4; (ii) a vertical seismic profiling (VSP) survey using the MiniVib source close to the well head with DAS recording in PITOP4; and  (iii) recordings of the seismic wavefield generated by P- and S-wave vibratory sources using surface DAS arrays in linear and helicoidal configurations, together with co-located 3D geophones for comparison.

DAS data were acquired with multiple gauge lengths and acquisition settings. The resulting datasets enable a systematic evaluation of acquisition parameters selection and highlight processing strategies required for different DAS configurations. They provide a valuable basis for assessing optimal DAS acquisition strategies for small-scale seismic applications and for defining processing workflows adapted to diverse source and receiver geometries.

The present study is being carried out within the framework of the USES2 project, which receives funding from the EUROPEAN RESEARCH EXECUTIVE AGENCY (REA) under the Marie Skłodowska-Curie grant agreement No 101072599.

This research has been supported by the Interdepartmental Research Center for Cultural Heritage CIBA (University of Padova) with the World Class Research Infrastructure (WCRI) SYCURI—SYnergic strategies for CUltural heritage at RIsk, funded by the University of Padova.

How to cite: Nesterova, O., Schenato, L., Constantinou, A., Le Dû, T., Meneghini, F., Travan, A., Bellezza, C., Michaud, G., Marzona, A., Brovelli, A., Zampato, S., Cassiani, G., Boaga, J., and Barone, I.: Distributed Acoustic Sensing at the Engineering Scale: Experimental Insights from the PITOP Test Site, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13235, https://doi.org/10.5194/egusphere-egu26-13235, 2026.

EGU26-13235

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How to cite: Pavez Orrego, C., Duda, M., Urozayev, D., Dupuy, B., and Barbosa, N.: Storm Amy observations with fibre-optic DAS data at the Svelvik CO₂ Field Lab, Norway: Implications for Monitoring and Networks , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10676, https://doi.org/10.5194/egusphere-egu26-10676, 2026.

EGU26-10676

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The WAVE seismic network is a dense, multi-instrument monitoring system deployed on a scientific campus in Hamburg, Germany. It combines seismometers, geophones, and a 19 km distributed acoustic sensing fiber loop installed in existing telecommunication infrastructure. The network covers large-scale research facilities including the European X-ray Free-Electron Laser (EuXFEL) and particle accelerators at DESY. Its primary goal is to characterise natural and anthropogenic ground vibrations and to quantify how these signals couple into ultra-precise measurement infrastructures that are limited by environmental noise. Beyond local applications, WAVE serves as a testbed for fibre-optic sensing concepts relevant to fundamental physics, including seismic and strain monitoring for gravitational wave detection.

The EuXFEL is a femtosecond X-ray light source designed for ultrafast imaging and spectroscopy. Its performance depends critically on precise timing and synchronisation of the electron bunches along the linear accelerator. Measurements of bunch arrival times reveal significant noise contributions in the 0.05–0.5 Hz frequency band, with peak-to-peak timing jitter of up to 25 femtoseconds. Using distributed acoustic sensing data, we demonstrate that this jitter is largely explained by secondary ocean-generated microseism, which is identified as a significant limiting factor for stable, high-precision XFEL operation in the sub-Hz regime. 

To assess the potential for prediction and mitigation, we investigate whether ocean wave activity in the North Atlantic can be used to anticipate microseismic signals observed at the EuXFEL site. Output from the WAVEWATCH III ocean wave model is used to generate synthetic Rayleigh wave spectrograms with the WMSAN framework. These are compared to seismic observations at the EuXFEL injector. By subdividing the North Atlantic into source regions, we evaluate their relative contributions to the observed seismic wavefield. While absolute amplitude prediction remains challenging, the modelling reproduces key spectral characteristics and temporal variability.

Our results demonstrate that combining dense fibre-optic sensing with physics-based ocean wave modelling provides a framework to characterise microseismic noise and assess its limiting impact on high-precision experiments. This approach supports noise mitigation efforts at high-precision accelerator facilities and is directly relevant to future ground-based gravitational wave detectors.

How to cite: Hadziioannou, C., Genthe, E., Kreutzer, S., Schlarb, H., Hoffmann, M., Gerberding, O., and Isleif, K.-S. and the the WAVE initiative: Distributed acoustic fibre sensing for large scientific infrastructures: ocean microseism at the European XFEL, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20683, https://doi.org/10.5194/egusphere-egu26-20683, 2026.

EGU26-20683

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Fibre-optic sensing technology is transforming seafloor monitoring by enabling dense, continuous measurements across vast distances using existing telecommunication infrastructure. Distributed acoustic sensing (DAS) and optical interferometry [1] have demonstrated remarkable potential for earthquake detection, ocean dynamics monitoring, and hazard early warning. However, for these technologies to be used for these applications, the transfer function between environmental perturbations and measured optical signal changes in submarine cables needs to be known.

We present the, to the best of our knowledge, first controlled-environment characterisation of submarine cable responses to active seismic and acoustic sources, comparing DAS and optical interferometry measurements with ground-truth data from 58 geophones, 20 three-component seismometers, and microphones [2]. Our results reveal three key findings:

• In contrast with proposed theoretical models [3], our interferometric measurements show first-order sensitivity to broadside seismic sources, enabling localisation of arrivals along straight fibre links.
• We identify a previously unreported fast-wave phenomenon, attributed to seismic energy coupling into the cable's metal armour and propagating at velocities exceeding 3.5 km/s, significantly altering recorded waveforms.
• We compared measurements between adjacent fibres within the same cable. Results show significant discrepancies between the measured waveforms, which should be considered in applications operating in a similar frequency range as our tests.

These findings show the complexity of submarine cable mechanics and their impact on optical sensing performance. Understanding these processes is critical for calibrating transfer functions and improving the reliability of fibre-based geophysical observations.  In addition to these findings, we also discuss the limitations of our methodology, which primarily arise from the limited range of seismic source frequencies available. Our work presents a first step towards understanding the complex transfer function of environmental perturbations to optical signals in subsea cables, advancing the vision of large-scale, cost-effective Earth observation systems.

[1] Marra, G. et al. Optical interferometry–based array of seafloor environmental sensors using a transoceanic submarine cable. Science 376 (6595), 874–879 (2022)

[2] Fairweather, D.M., Tamussino, M., Masoudi, A. et al. Characterisation of the optical response to seismic waves of submarine telecommunications cables with distributed and integrated fibre-optic sensing. Sci Rep 14, 31843 (2024)

[3] Fichtner, A., Bogris, A., Nikas, T. et al. Theory of phase transmission fibre-optic deformation sensing. Geophysical Journal International, 231(2), 1031–1039, (2022)

How to cite: Tamussino, M., Fairweather, D. M., Masoudi, A., Feng, Z., Barham, R., Parkin, N., Cornelius, D., Brambilla, G., Curtis, A., and Marra, G.: Submarine Cable Optical Response to Seismic Waves: Insights from Controlled-Environment Tests, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7247, https://doi.org/10.5194/egusphere-egu26-7247, 2026.

EGU26-7247

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Optical interferometry on submarine fiber-optic telecommunication cables offers a transformative opportunity for offshore geohazard monitoring by providing continuous measurements of seafloor perturbation at useful intervals over trans-oceanic distances (Marra et al., 2022). We analyze a southwest Pacific subset of data from a section of the Southern Cross NEXT cable connecting Auckland (New Zealand) to Alexandria (Australia). Using only cable-based measurements, we image the seismic rupture kinematics of the 17 December 2024 Mw 7.3 Vanuatu earthquake, the largest seismic event recorded on this cable since its installation.

We analyze measurements of a section of cable more than 1,000 km in length and comprising 18 inter-repeater spans including the section that runs roughly parallel to the Vanuatu subduction zone and the adjoining section extending southward toward New Zealand. The earthquake produces clear and coherent arrivals in the optical frequency deviation recorded across multiple spans, with well-defined signatures visible in both time series and spectrograms. We first extract earthquake-related strain signals in the 0.1-0.3 Hz frequency band and apply the Multiple Signal Classification (MUSIC) back-projection technique to recover the source-time evolution of the rupture. The inferred rupture is predominantly bilateral and consistent with the USGS finite-fault solution, confirming that interferometric submarine cables can function as effective regional seismic arrays for rapid characterization of offshore earthquakes.

These results further demonstrate the capability of submarine fiber-optic cables to image earthquake rupture processes using high-frequency strain signals, providing valuable monitoring coverage, especially in instrumentally sparse regions such as the southwest Pacific. By resolving rupture kinematics directly, cable-based observations offer a pathway toward improved tsunami early-warning strategies that rely less on empirical magnitude–scaling relations, which are uncertain for large earthquakes. Planned upgrades of the interrogating laser will allow the performance of this approach to be assessed at lower frequencies, where cable-based observations may provide direct constraints on tsunami propagation and other long-period geophysical processes.

How to cite: A. Naeini, A., Fry, B., Marra, G., Tamussino, M., Grand, J., D. Eccles, J., van Wijk, K., Veverka, D., and Pandit, R.: Optical Interferometry-based seafloor cable Measurements for Rupture Imaging and Tsunami Signal Analysis in the Southwest Pacific, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-893, https://doi.org/10.5194/egusphere-egu26-893, 2026.

EGU26-893

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A seismic observation using Distributed Acoustic Sensing (DAS) using seafloor cable can provide spatially high-density data for a long distance in marine areas. A seafloor seismic and tsunami observation system using an optical fiber cable off Sanriku, northeastern Japan was deployed in 1996. Short-term DAS measurements were sporadically repeated since February 2019 using spare fibers of the Sanriku system (Shinohara et al., 2022). A total measurement length is approximately 100 km.  It has been concluded that measurement with a sampling frequency of 100 Hz, a ping rate of 500 Hz, gauge length of 100 m, and a spatial interval of 10 m is adequate for earthquake and tsunami observation.  From March 2025, we started a continuous DAS observation to observe seismic activity. When the continuous DAS observation was commenced, we developed quasi real time data transmission system through the internet. Because a DAS measurement generates a huge mount of data per unit time and capacity of internet is limited, decimation for spatial direction is adopted. In addition, data format is converted from HDF5 to conventional seismic data exchange format in Japan (win format). An interrogator generates a HDF5 file every 30 seconds. After the file generation, the telemetry system reads the HDF5 file, and decimates data for spatial domain. Then, the data format is changed to the win format and the data are sent to the internet. In other words, data transmission is delayed for a slightly greater than 30 seconds. Data with the win format can be applied to various seismic data processing which has been developed before. To locate a hypocenter using DAS data, seismic phases in DAS data must be identified. To evaluate performance of hypocenter location using DAS records, arrival times of P- and S-waves were picked up on the computer display for local earthquakes. Every 100 channel records on DAS data and data from surrounding ordinary seismic stations were used. Location program with absolute travel times and one-dimensional P-wave velocity structure was applied. Results of location of earthquakes were evaluated by mainly using location errors. Errors of the location with DAS data were smaller than those of the location without the DAS data. Increase of arrival data for DAS records seems to be efficient to improve a resolution. However, picking up signals for all channels (seismic station) manually are costly due to a large number of channels. To expand the location method, an improved automatic pick-up program using evaluation function from conventional seismic network data by seismometers for DAS data (Horiuchi et al., 2025) was applied to the DAS data obtained by the Sanriku system. As a result, arrivals time of P, S and converted PS waves can be precisely identified with high resolution. We have a plan to locate earthquakes using all DAS channels (seismic stations)  and surrounding ordinary marine and land seismic stations.

How to cite: Shinohara, M., Fukushima, S., Uehira, K., Asano, Y., Tanaka, S. S., and Otsuka, H.: Seismic data telemetry system and precise hypocenter location for distributed acoustic sensing observation using seafloor cable off Sanriku, Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4163, https://doi.org/10.5194/egusphere-egu26-4163, 2026.

EGU26-4163

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A recently developed multispan distributed acoustic sensing (multispan-DAS) technique from Nokia Bell Labs enables strain measurements along submarine fiber-optic cables across multiple repeater-separated spans. By leveraging the high-loss loopback couplers within optical repeaters, this technique overcomes the long-standing limitation of conventional DAS to the first span of a repeated cable, typically < 100 km offshore. Dense, continuous arrays of seafloor strain sensors can now extend to hundreds or thousands of kilometers. This technique has been used to successfully record the 2025 M8.8 Kamchatka earthquake and tsunami at teleseismic range with a spatial resolution of ~100 m across 4400 km of a repeated submarine cable.

In November 2025, the multispan-DAS system from Nokia Bell Labs was deployed for three months on both repeated submarine cables of the Ocean Observatories Initiative Regional Cabled Array (OOI RCA) offshore Oregon. The deployment traverses the Cascadia subduction zone forearc and extends approximately 500 km offshore to Axial Seamount. During this period, the first span of the southern cable was simultaneously interrogated using a multiplexed conventional DAS unit, while data continued to stream from co-located cabled seismometers, hydrophones, and other oceanographic instruments on the OOI RCA.

The multispan-DAS system recorded a regional earthquake beyond the first repeater of both cables during testing as well as the ambient seafloor seismic wavefield, demonstrating sensitivity to a broad range of seismic, oceanographic, and acoustic signals. These observations provide a unique opportunity to directly compare multispan-DAS measurements with conventional DAS and established seafloor instrumentation across a large spatial extent. The resulting dataset will be publicly released following documentation and quality control. We will present preliminary results characterizing the noise floor, sensitivity, and signal fidelity of multispan-DAS relative to co-located sensors, and examine the consistency of observed seismic and oceanographic signals across measurement modalities. These results will highlight the potential of multispan-DAS for applications including routine earthquake monitoring, earthquake early warning, and broader seafloor observation, and represent an important step toward establishing this technique as a new tool for the seismological and oceanographic communities.

How to cite: Krauss, Z., Lipovsky, B., Mazur, M., Wilcock, W., Fontaine, N., Ryf, R., Rose, A., Dientsfrey, W., Abadi, S., Denolle, M., and Hartog, R.: Toward Global-Scale Submarine Fiber Sensing: Early Results from Multispan DAS at the OOI Regional Cabled Array, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15142, https://doi.org/10.5194/egusphere-egu26-15142, 2026.

EGU26-15142

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Seismic ambient noise is a ubiquitous and constant resource, ideal for non-invasive investigations of the solid earth. Coastlines around the world are handling an increase in coastal erosion due to sea level rise and more energetic storms. Monitoring this is becoming an increasingly necessary task to protect coastal settlements. Using Distributed Acoustic Sensing in seismic monitoring has already shown incredible potential and offers the advantage of dense measurements. Our project seeks to identify the efficacy of Distributed Acoustic Sensing for monitoring subsurface changes which precede cliff failure. We present early findings from the first long-term deployment of a fibre optic cable along the coastline - North Sea, Norfolk, UK. We investigate differences in signal characteristics between conventional seismometers and Distributed Acoustic Sensing in this setting, and interpret the seismic signatures of key sources in the area. This deployment was recording for 22 months, allowing us to monitor both short-term and seasonal changes. We identify the frequency ranges excited by storm events (0.2 - 1 Hz), the dominance of short-period secondary microseismic activity, and the importance of local sea state and weather on influencing higher frequency signals. We also discuss limitations of Distributed Acoustic Sensing and the sources it can not reliably capture when compared to broadband seismometers and nodal geophones. We conclude by discussing how this noise analysis affects the use of ambient noise tomography for seismic velocity monitoring. Future research will test the efficacy of such applications, with the hope of providing better estimates of coastal recession and identifying hazardous areas on a metre-scale.

How to cite: Whitelam, H., Bie, L., Johnson, J., Payo Garcia, A., and Chambers, J.: Coastal Ambient Noise and Microseismic Monitoring with Distributed Acoustic Sensing: a Case Study from Norfolk, UK, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7298, https://doi.org/10.5194/egusphere-egu26-7298, 2026.

EGU26-7298

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Combining traditional seismic networks with Distributed Acoustic Sensing (DAS) to record ground-motion on telecommunications cables provides new opportunities to study small earthquakes with unprecedented spatial and temporal resolution. Here we present a detailed study of an earthquake sequence offshore northwest of Kefalonia island, Greece that began in March 2024 and returned to background levels by November–December. The sequence was recorded by both a permanent seismic network for its duration and by DAS on a fiber-optic telecommunications cable between 1 - 15 August 2024.  The two-week DAS dataset provides continuous strain measurements along ~15 km of optical fiber between northern Kefalonia and Ithaki during a period that captured elevated seismic activity. Combining seismic station and DAS data reveals distinct physical features of the sequence that are not observable with seismic stations alone, including details of mainshock-aftershock clustering and well-resolved source spectra at frequencies of up to ~50 Hz for M < 3 events. The signal-to-noise-ratio > 3 at frequencies of up to 50 Hz observed on DAS waveforms for a representative group of events suggests consistency with typical earthquake stress-drop values that range from 1-10 MPa. It further suggests that DAS data may be used to augment detailed studies of microearthquake source parameters.

We apply semblance-based detection to DAS waveforms and manually inspect 5,734 earthquakes that occurred within ~50 km of the fiber to build an initial earthquake catalog. We then combine DAS and seismic-station data to locate 284 events with high signal-to-noise ratios and compute their local magnitudes with seismic station data to create a detailed subset of the initial catalog. We apply waveform cross-correlation to offshore DAS data for events in the detailed catalog to associate unlocated detections with template events and estimate relative magnitudes from amplitude ratios and further enhance the detailed catalog. This approach adds an additional 2,496 earthquakes (2,780 events in total) with assigned locations and magnitudes and leads to an enhanced catalog with completeness magnitude M_c = -0.5. Most earthquakes (2,718 of 2780) cluster within a ~5 km radius approximately 10 km offshore of northwestern Kefalonia and exhibit local rates exceeding 100 events per hour.

Our enhanced catalog provides a detailed spatiotemporal record of seismicity in a region with limited station coverage and demonstrates the effectiveness of integrating DAS with seismic networks for earthquake monitoring of active seismic sequences. Furthermore, it resolves details of mainshock–aftershock clustering that would have otherwise likely have been erroneously classified as swarm-like with standard monitoring, highlighting how observational resolution influences the interpretation of the physics driving earthquake sequences.

How to cite: Harrington, R. M., Bocchini, G. M., Bozzi, E., Roth, M. P., Gaviano, S., Pascucci, G., Grigoli, F., Biondi, E., and Sokos, E.: Using a hybrid seismic and Distributed Acoustic Sensing (DAS) network to study microseismicity in high spatiotemporal resolution offshore of Kefalonia Island, Greece , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4254, https://doi.org/10.5194/egusphere-egu26-4254, 2026.

EGU26-4254

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Distributed Acoustic Sensing (DAS) transforms fiber-optic cables into ultra-dense strainmeter arrays, providing spatially and temporally continuous earthquake recordings. While its potential for offline seismic characterization is increasingly recognized, a key application of this sensing paradigm is real-time monitoring for Earthquake Early Warning (EEW). The use of existing fiber-optic infrastructures allows for sensing cables located close to seismogenic sources, such as offshore subduction zones, potentially extending the lead time of issued alerts. DAS deployments within Near Fault Observatories further provide dense spatial coverage of epicentral areas, favouring the rapid extraction of robust source information.

The application of DAS to EEW – alone or as a complement to standard accelerometers - has been recently explored, specifically focusing on the estimate of earthquake magnitude from the first seconds of recorded data. Existing approaches rely either on conversion strategies to ground-motion proxies or on direct analysis in the strain-rate domain. However, both the robustness of different conversion strategies and the selection of the most informative physical quantity for early magnitude estimation are not yet consolidated. In offshore environments, additional complexity arises from fiber-optic cables deployed on sediments, where strong converted phases often dominate early waveforms and hinder the direct P-wave signal traditionally used for EEW.

In this work, we analyse earthquakes recorded by the ABYSS network, supported by the ERC – starting program, consisting of 450 km of offshore telecommunication cables deployed along the Chilean subduction trench and interrogated by three DAS units. At this high-seismicity testbed, we develop a strategy for fast magnitude estimation with DAS. We show that converted Ps phases preceding S-wave arrivals carry significant information on earthquake magnitude. Furthermore, we investigated whether the use of time and space-integrated observables on DAS recordings can enhance the predictive power of amplitudes from the first seconds of seismic signals.

Finally, we assess the performance of a DAS-based EEW, grounded on the software PRESTo (Satriano et al., 2011). Using moderate-to-large offshore Chilean earthquakes, we highlight potential and limitations of DAS in regions with sparse conventional instrumentation. Complementary analyses using data from the Irpinia Near Fault Observatory demonstrate the benefits of jointly exploiting DAS and traditional seismic stations within dense monitoring networks, confirming the applicability of DAS-based EEW systems across different tectonic settings.

How to cite: Strumia, C., Festa, G., Trabattoni, A., Rivet, D., Elia, L., Carotenuto, F., Colombelli, S., Scala, A., Scotto di Uccio, F., and Suresh, A.: Strategies and Challenges in Applications of DAS-based Earthquake Early Warning Systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12675, https://doi.org/10.5194/egusphere-egu26-12675, 2026.

EGU26-12675

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Monitoring fin whale (Balaenoptera physalus) vocalizations is of significant scientific importance and practical value for marine ecology, hydroacoustics, and geophysics. Conventional monitoring approaches, such as hydrophone arrays, ocean-bottom seismometers (OBS), and satellite tagging, are limited by sparse spatial coverage, potential biological disturbance, and high costs. Distributed acoustic sensing (DAS) is an emerging technology that utilizes submarine optical cables as dense acoustic arrays, providing opportunities for large-scale, high-resolution monitoring of whale vocalizations. Here, we reveal the wavefield features of fin whale vocalizations by integrating DAS observational data combined with numerical simulations. Three distinct features—Insensitive response segment (IRS), high-frequency component loss, and acoustic notch—were identified in the observed wavefield. DAS response analysis via ray-acoustic modeling indicates that the length of the IRS is positively correlated with the vertical source-to-cable distance, while the gauge length is responsible for the high-frequency loss in Type-B calls. Furthermore, wavefield simulations using the spectral-element method (SEM) demonstrate that the acoustic notches represent transitions between transmission zones of waterborne multipath waves entering the seafloor, exhibiting high sensitivity to the seafloor P-wave velocity, water depth, and topography. These findings not only enhance our understanding of the DAS-observed wavefields, but also highlight the potential of utilizing DAS and acoustic notches for ocean environmental parameter estimation.

How to cite: Wang, Q.: Revealing the Wavefield Features of Fin Whale Vocalizations Observed by Distributed Acoustic Sensing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4625, https://doi.org/10.5194/egusphere-egu26-4625, 2026.

EGU26-4625

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Ice streams are major contributors to ice sheet mass loss and critical regulators of sea level change. Despite their important, standard viscous flow simulations of ice stream deformation and evolution have limited predictive power, mostly because our understanding of the involved processes is limited. This leads, for instance, to widely varying predictions of sea level rise during the next decades.

Here we report on a Distributed Acoustic Sensing experiment conducted in the borehole of the East Greenland Ice Core Project (EastGRIP) on the Northeast Greenland Ice Stream. For the first time, our observations reveal a brittle deformation mode that is incompatible with viscous flow over length scales similar to the resolution of modern ice sheet models: englacial ice quake cascades that are not being recorded at the surface. A comparison with ice core analyses shows that ice quakes preferentially nucleate near volcanism-related impurities, such as thin layers of tephra or sulfate anomalies. These are likely to promote grain boundary cracking, and appear as a macroscopic form of crystal-scale wild plasticity. A conservative estimate indicates that seismic cascades are likely to produce strain rates that are comparable in amplitude to those measured geodetically, thereby bridging the well-documented gap between current ice sheet models and observations.

How to cite: Fichtner, A., Hofstede, C., Kennett, B., Svensson, A., Westhoff, J., Walter, F., Ampuero, J.-P., Cook, E., Zigone, D., Jansen, D., and Eisen, O.: Englacial ice quake cascades in the Northeast Greenland Ice Stream - Observations and implications of ice stream dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5156, https://doi.org/10.5194/egusphere-egu26-5156, 2026.

EGU26-5156

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In recent years, Distributed Acoustic Sensing (DAS) has emerged as a cost-effective seismic monitoring tool for cryosphere research. Compared to conventional geophone arrays, the DAS system is compact, easy to transport, and can be rapidly deployed over large distances in glaciated environments.

Previous studies have demonstrated that DAS is a useful tool for ice-sheet imaging and monitoring glacier dynamics. For example, using borehole DAS in conjunction with surface explosives (e.g., Booth et al., 2022; Fitchner et al., 2023) or passive recordings using surface DAS (e.g., Walter et al., 2020; Gräff et al, 2025). Significant progress has been made in applying surface DAS for active marine subsurface imaging (e.g., Pedersen et al., 2022; Raknes et al., 2025). We extend this approach to active englacial and subglacial imaging on Slakbreen, Svalbard.

During a multi-geophysical field campaign in March 2025, we acquired seismic data using surface explosives along an approximately 2 km fibre co-located with a vertical-component geophone array. We process different reflected modes (PP and PS) recorded on the fibre and benchmark the imaging results against the equivalent PP-image from the geophone array. We evaluate differences in wavefield sensitivity across the three datasets and we will present how these can be used to characterise the state of the cryosphere and deeper sedimentary successions.

Despite the relative immaturity of DAS for glacier imaging and current limitations of the processing workflow, our results clearly establish surface DAS as a viable monitoring tool for seismic imaging of the cryosphere and as a potential enabler of large-scale seismic monitoring of glaciers and the subsurface.

References:

Booth, A. D., P. Christoffersen, A. Pretorius, J. Chapman, B. Hubbard, E. C. Smith, S. de Ridder, A. Nowacki, B. P. Lipovsky, and M. Denolle, 2022, Characterising sediment thickness beneath a greenlandic outlet glacier using distributed acoustic sensing: preliminary observations and progress towards an efficient machine learning approach: Annals of Glaciology, 63(87-89):79–82.                                                                                                                                                   

Fichtner, A., C. Hofstede, L. Gebraad, A. Zunino, D. Zigone, and O. Eisen, 2023, Borehole fibre-optic seismology inside the northeast greenland ice stream: Geo-physical Journal International, 235(3):2430–2441.

Gräff, D., B. P. Lipovsky, A. Vieli, A. Dachauer, R. Jackson, D. Farinotti, J. Schmale, J.-P. Ampuero, E. Berg, A. Dannowski, et al., 2025, Calving-driven fjord dynamics resolved by seafloor fibre sensing: Nature, 644(8076):404–412.

Pedersen, A., H. Westerdahl, M. Thompson, C. Sagary, and J. Brenne, 2022, A north sea case study: Does das have potential for permanent reservoir monitoring? In Proceedings of the 83rd EAGE Annual Conference & Exhibition, pages 1–5. European Association of Geoscientists & Engineers.

Raknes, E. B., B. Foseide, and G. Jansson, 2025, Acquisition and imaging of ocean-bottom fiber-optic distributed acoustic sensing data using a full-shot carpet from a conventional 3d survey: Geophysics, 90(5):P99–P112.

Walter, F., D. Gräff, F. Lindner, P. Paitz, M. Köpfli, M. Chmiel, and A. Fichtner,2020, Distributed acoustic sensing of microseismic sources and wave propagation in glaciated terrain: Nature communications, 11(1):2436.

How to cite: Myklebust, T. H., Landrø, M., Rørstadbotnen, R. A., and Robinson, C.: Seismic Characterisation of an Arctic Glacier, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13921, https://doi.org/10.5194/egusphere-egu26-13921, 2026.

EGU26-13921

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Over the past years, a wide range of machine learning–based phase picking methods have been developed, primarily targeting three-component seismometer data from tectonic earthquakes. With the rapid growth of distributed acoustic sensing (DAS) applications, diversification of use cases, and availability of increasingly large DAS datasets, these methods are now being applied to single-component DAS recordings. However, their optimal use for DAS data and for alternative signal types such as cryoseismological events, remains rarely explored.
In this study, we present a systematic analysis of the performance of machine learning–based phase picking methods pretrained on tectonic earthquakes on one-component cryoseismological DAS data obtained on the Rhône Glacier in the Swiss Alps in July 2020. We evaluate multiple strategies for generating pseudo-three-component data from the intrinsically single-component DAS strain-rate data, including zero-padding of missing components, duplication of the single component, and the use of consecutive DAS channels as surrogate components. In addition, we assess the phase-picking performance across different preprocessing schemes, comparing conservatively band-pass filtered data with denoised data obtained using a J-invariant  autoencoder specifically trained on cryoseismological DAS data. Finally, we analyze the spatial and temporal distribution of located events over the full observation period and across the entire glacier. Event clusters are correlated with weather conditions, daily cycles, and the geometry of the glacier bed to explore potential patterns in cryoseismic activity.
Our results indicate that treating consecutive DAS channels as surrogate components yields the most reliable phase-picking performance, whereas extensive denoising can degrade picking accuracy. We further discuss spatial clusters of event locations and their correlations with glacier topography and meteorological conditions.

How to cite: Zitt, J., Isken, M., Münchmeyer, J., Gräff, D., Fichtner, A., Walter, F., and Umlauft, J.: Best Practices for Machine Learning based Icequake Picking with Distributed Acoustic Sensing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12160, https://doi.org/10.5194/egusphere-egu26-12160, 2026.

EGU26-12160

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The current phase of unrest of the Campi Flegrei caldera (Italy), one of the most dangerous volcanic complexes in the world, requires increasingly rapid and high-resolution seismic monitoring solutions. In this context, Distributed Acoustic Sensing (DAS) has recently emerged as a highly innovative technology, enabling existing fiber-optic cables to be repurposed into ultra-dense seismic arrays capable of sampling the seismic wavefield with unprecedented spatial resolution.

In this study, we present a new earthquake-localization method that uses automatically identified P- and S-wave arrivals on DAS data to localize seismic events. Employing Transformer-based architectures designed to process DAS's high-dimensional strain data, our approach simultaneously estimates key source parameters, including hypocentral location, magnitude, and origin time. A comparative analysis against the official seismic catalogue reveals minimal residuals, validating the model's robustness. 

The model therefore represents a significant advancement, as it enables reliable earthquake localization in extremely short time frames using exclusively automatically picked data, while simultaneously overcoming the computational bottlenecks typical of traditional processing workflows. As a result, this methodology establishes a new benchmark for real-time monitoring of magmatic and hydrothermal systems, substantially contributing to improved seismic hazard assessment.

How to cite: Corsaro, M., Seydoux, L., Currenti, G., Cannavò, F., Palazzo, S., Allegra, M., Jousset, P., Prestifilippo, M., and Spampinato, C.: Deep Learning-Based Earthquakes Localization at Campi Flegrei via Distributed Acoustic Sensing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13315, https://doi.org/10.5194/egusphere-egu26-13315, 2026.

EGU26-13315

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Very long period (VLP; 0.01-0.2 Hz) seismicity is observed at many volcanoes worldwide, and provides key insights into magma and fluid dynamics within volcanic structures. VLPs are typically recorded by sparse networks of seismometers, which limits the ability to resolve the resulting displacement (or deformation) at fine spatial scales. Distributed acoustic sensing (DAS) may help overcome this limitation by densely sampling the projection of the strain tensor along fibre-optic cables with high spatial and temporal resolution, enabling a more complete view of VLP-induced deformation. Here, we analyse VLP strain signals recorded by DAS at Stromboli volcano (Italy) in November 2022 along a 6-km dedicated fibre-optic cable. We designed the cable geometry to provide broad coverage of the craters and to sample the strain at multiple locations and along different directions. We focus on a dataset of approximately 200 VLP events recorded between November 13 and 14, 2022. The VLP strain signals correlate with explosive activity and show consistent features across multiple events, indicating a persistent, non-destructive source. Leveraging the distributed nature of DAS measurements, we recover the principal strain axes of VLPs and estimate both the location and the volumetric change of the source using a quasi-static deformation model. We retrieve the principal horizontal strains for each VLP by inverting strain amplitudes measured along three different fibre directions and at multiple locations along the cable, allowing us to resolve their spatial distribution. The resulting principal VLP strains exhibit radial and tangential orientations with respect to the craters, consistent with observed seismic particle motions and an axisymmetric source. We then model the VLP strain along the fibre using a point-like deformation source (Mogi). The optimal agreement between modeled and observed VLP strain averaged over the 200 events is for a point source located ~500 m beneath the active craters, with an estimated volumetric change of ~30 m³. Under the assumption of a spherical source with a radius of 87 m, the inferred volumetric change corresponds to a pressure change of ~19 kPa. These results are consistent with previous studies and highlight the capability of DAS to investigate volcano deformation at long periods.

How to cite: Biagioli, F., Stutzmann, E., Bernard, P., Métaxian, J.-P., Cayol, V., Lacanna, G., Delle Donne, D., Capdeville, Y., and Ripepe, M.: Distributed acoustic sensing of very long period strain signals from strombolian explosions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8383, https://doi.org/10.5194/egusphere-egu26-8383, 2026.

EGU26-8383

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Fibre-optic sensing technologies are rapidly transforming geophysical monitoring by enabling spatially dense, temporally continuous observations of seismic and acoustic wavefields in environments that are difficult to instrument with conventional sensors. In marine settings, Distributed Acoustic Sensing (DAS) applied to seabed fibre-optic cables offers new opportunities for low-impact monitoring of fluid and gas migration processes, which are fundamental both to volcanic–hydrothermal systems and to emerging offshore carbon capture and storage (CCS) applications.

In this study, we investigate the feasibility of marine DAS for detecting natural and artificial CO₂ bubble emissions in a shallow-water volcanic environment offshore Panarea (Aeolian Islands, Italy). Panarea hosts the OGS NatLab Italy, part of ECCSEL-ERIC, thanks to its active submarine degassing associated with a hydrothermal system and therefore represents a natural laboratory and an analogue site for potential subseabed CO₂ leakage scenarios. A 1.1-km-long armored fibre-optic cable was deployed on the seabed and interrogated using two different DAS systems, providing continuous passive acoustic and seismic recordings. To support signal identification and interpretation, the DAS data were complemented by controlled gas releases from scuba tanks, by a High Resolution Seismic (boomer) survey and side-scan sonar imaging, to characterize seabed morphology and shallow subsurface structures along the cable route.

The DAS recordings revealed acoustic signatures associated with both natural CO₂ bubble emissions and controlled artificial releases. Bubble-related signals were detected as localized, temporally variable acoustic responses along the fibre, demonstrating the sensitivity of DAS to gas-driven processes at the seabed. The integration of passive DAS monitoring with active seismic imaging techniques enabled a more robust interpretation of observed signals and seabed processes.

From an Earth sciences perspective, these results demonstrate that marine DAS can serve as a low-impact, spatially continuous monitoring tool for submarine volcanic and hydrothermal systems, complementing traditional geochemical sampling and visual observations and offering new insights into the temporal variability of degassing activity. Beyond natural systems, the demonstrated capability of DAS to detect bubble-related acoustic signals has direct implications for offshore CCS, where early detection of CO₂ leakage is critical for storage integrity and environmental safety.

Overall, this field-scale experiment highlights the potential of fibre-optic sensing to address key challenges in marine monitoring, and underscores the value of integrated approaches for studying fluid and gas migration processes.

Acknowledgements:

• ECCSELLENT project (“Development of ECCSEL - R.I. ItaLian facilities: usEr access, services and loNg-Term sustainability”)
• ITINERIS - Italian Integrated Environmental Research Infrastructures System - Next Generation EU Mission 4, Component 2 - CUP B53C22002150006 - Project IR0000032
• Panarea NatLab Italy: https://eccsel.eu/catalogue/facility/?id=124
• ECCSEL: https://eccsel.eu/

References:

• Detection of CO2 emissions from Panarea seabed with Distributed Acoustic Sensing (DAS): a preliminary investigation. Meneghini et al. OGS report (2025).
• Marine Fiber-Optic Distributed Acoustic Sensing (DAS) for Monitoring Natural CO₂ Emissions: A Case Study from Panarea (Aeolian Islands, Italy). Bellezza et al. Upon submission to Applied Sciences (2026).

How to cite: Bellezza, C., Meneghini, F., Travan, A., Baradello, L., Deponte, M., and Schleifer, A.: Marine Distributed Acoustic Sensing (DAS) for Detection of Submarine CO₂ Bubble Emissions: Insights from a Shallow-Water Volcanic Setting at Panarea (Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7462, https://doi.org/10.5194/egusphere-egu26-7462, 2026.

EGU26-7462

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Etna is the largest, most active and closely monitored volcano in Europe,
making it a crucial study region for volcanology and geohazard assessment. In early
July 2019, a 1.5 km fibre-optic cable was deployed near the summit of Mount Etna
and interrogated for two months. The cable was divided into four main segments, two
of which point towards different active crater areas. Temporary seismic broadband
stations and infrasound sensors were also deployed along the cable. During the
experiment, three distinct eruptive events were recorded. The first two events are
characterised by a large number of explosions in the active crater area, together with
an increase in background tremor activity. The third event is characterised by a larger
increase in background tremor, but almost no explosions.

The continuous recordings are analysed in the frequency-wavenumber domain,
which reveals the features of the background tremor activity and the stacked transient
signals, such as explosions. During the first two eruptive events, the stack of
explosive sources is characterised by a non-dispersive arrival, travelling with
different apparent velocities along each segment, and a non-linear ground response up
to 25 Hz. These segments can be used as an antenna to estimate an average back-
azimuth for the explosions, which come from the same crater area during both
eruptive events.

Outside of the three eruptive events, the background tremor features two slow
dispersion modes, both well resolved on the raw recordings. The slowest mode is
affected by gauge-length attenuation at higher frequencies, due to its short
wavelength, but remains detectable up to 27 Hz, with group velocities as low as 170
m/s. These observations showcase the utility of simple, rectilinear geometries in
deployments despite their known shortcomings, such as in location procedures. For
known source regions, such as volcanoes, a well-oriented segment can leverage
continuous activity to record the incoming wavefield and extract dipersion curves
without the need to perform cross-correlations, simplifying the workflow.

How to cite: Latorre, H., Diaz-Meza, S., Jousset, P., Ventosa, S., Ugalde, A., Currenti, G., and Bartolomé, R.: Spectral analysis of background and transient signals at Mount Etna using rectilinear fibre-optic segments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5274, https://doi.org/10.5194/egusphere-egu26-5274, 2026.

EGU26-5274

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NORFOX is a purpose-built fibre-optic Distributed Acoustic Sensing (DAS) installation located in southeastern Norway, approximately 150 km north of Oslo. Beyond its primary function of monitoring earthquakes and explosions, the system captures a broad range of other signals, including aircraft, thunder, and atmospheric phenomena. A key advantage of NORFOX is its overlap with the co-located NORES seismometer array, which enables direct calibration of DAS measurements against conventional seismic recordings and supports method development under well-constrained ground-truth conditions. In this contribution, we introduce the NORFOX infrastructure and array layout, discuss key design choices, and summarize practical strengths and limitations using representative examples.

NORFOX is additionally equipped with all-sky cameras operated by Norsk Meteor Nettverk for meteor monitoring, which also capture nearby lightning activity. Lightning locations provide independent timing and spatial context that help interpretation coincident acoustic signatures observed on the fibre. Together with weather information, noise-floor characterization, and optical monitoring, these observations provide a benchmark dataset for both existing and future DAS installations and calibration

We also present in-house approaches to reduce noise, understanding signals, strategies on managing data volumes and edge-computing. Furthermore, we show and interpret signals from nearby quarry blasts, regional earthquakes, thunderstorms, and aircraft. Finally, we demonstrate and evaluate DAS array-processing methodologies for earthquake and explosion monitoring at NORFOX. Overall, dedicated research fibre arrays such as NORFOX provide a controlled environment to develop, benchmark, and calibrate DAS-based monitoring workflows in combination with co-located seismic instrumentation.

How to cite: Turquet, A., Wuestefeld, A., Baird, A., Iranpour, K., and Rydtun, R.: Reimagining Seismic Array Processing with Fibre-Optic DAS: The NORFOX Array, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17223, https://doi.org/10.5194/egusphere-egu26-17223, 2026.

EGU26-17223

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The detection of nanoseismicity (very tiny earthquakes sometimes associated with small cracks in rock, also called acoustic emissions) is an important area of research aiding in the understanding of geophysical processes, hazard detection, material failure and human-driven nanoseismicity. The high frequency and attenuation of nanoseismicity require high-frequency monitoring within metres of the source to capture the event. This has made them difficult to monitor in conditions outside of small-scale lab experiments, in which failure is intentionally induced. The development of distributed acoustic sensing (DAS) as a new tool for seismic monitoring, however, has increased the feasibility of investigating such signals in the field due to its high temporal and spatial resolution. Manual picking of these events, while possible, is impractical for long-term deployments and for time-critical applications such as stability monitoring, which limits the utility of the technology. Automation of the detection of nanoseismic events within such data is therefore essential for the long-term processing of DAS data and real-time processing of data for use in stability monitoring.  

We have developed a pipeline for the automated extraction of nanoseismic events from DAS data, using a new, simple ratio technique called Spatial Short-Term Average (SSTA). The pipeline takes an input of DAS data and generates a series of windows within the data containing information about high amplitude signals relating to nanoseismicity.  

Using the automatically detected events, we labelled the windows to train a series of machine learning models to classify the different signals. Once trained, we evaluated the performance of the various models to select the most effective method for processing the collected data. The best performing models will then be tested at scale with the resulting classified dataset being plotted spatially along the length of the deployment to identify patterns of activity across space and time. 

How to cite: Seager, D., Johnson, J., Bie, L., De La Iglesia, B., and Milner, B.: Automatic detection and classification of Nanoseismicity in Distributed Acoustic Sensing data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-211, https://doi.org/10.5194/egusphere-egu26-211, 2026.

EGU26-211

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Interpreting amplitudes in Distributed Acoustic Sensing (DAS) data is challenging because the recorded signal is influenced by multiple factors.

To differentiate the impact of fiber orientation from site effects, we develop expressions of axial strain for different body wave polarizations. These expressions consider a linear fiber segment with any orientation in space. From these we explore array geometry properties and the potential of the DAS transfer function as a polarization filter. This last property arises from the polarity inversion characteristic of shear waves and the averaging nature of the gauge length. If the gauge length is set to be a loop instead of a linear segment then the DAS will average all azimuth for a horizontal loop, canceling SH waves. For a vertical loop, all dips are averaged canceling SV waves traveling within the loop plane. These results could reflect a link between DAS and rotational seismology. 

From these transfers functions, we develop a low-cost forward model based on ray theory that predicts amplitude recorded in a DAS array. Differences in amplitude between the modeled and observed wavefields relate to local site amplification from which, we create an amplitude correction factor. We evaluated this method using active seismic experiments from the PoroTomo dataset, successfully identifying regions with anomalous high amplitude responses consistent with the recordings following a magnitude 4.3. 

The results, together with the main elements of our approach, are transferable in many new sensing strategies, including optimization of fiber deployment geometry, generations of synthetic data and the acceleration and improvement of existing location methods through DAS-specific amplitude and phase corrections.
In summary, by exploiting the known directional sensitivity of DAS, we draw new insights from amplitude variations along the fiber array, treating energy loss as equally informative as energy gain in interpreting the wavefield. 

How to cite: Fontaine, O., Fichtner, A., Hudson, T., Lecocq, T., and Caudron, C.: Understanding fiber optic sensitivity to a wavefield: A framework to separate site amplification from orientation effects, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12609, https://doi.org/10.5194/egusphere-egu26-12609, 2026.

EGU26-12609

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We present a back-projection based earthquake location method tailored to Distributed Acoustic Sensing (DAS) arrays, using short overlapping fiber segments and a combined P–S framework to reliably locate local earthquakes. A 66km quasi-linear telecommunication fiber in Israel was repurposed as a DAS array. We analyzed several local earthquakes with varying source–array geometries. We divided the fiber into overlapping 5.4 km segments and back-projected P- and S-wave strain-rate recordings using a local 1D velocity model over a regional grid of potential earthquake locations. Each grid point is assigned with P- and S-phase semblance, and the corresponding phase-specific origin times, associated with the timing of maximum semblance. Segment-specific P- and S-phase semblance maps and the difference between P and S origin times were combined through a weighting scheme that favors segments with spatially compact high-semblance regions. The objective is maximizing both P- and S-wave semblance and minimizing P- and S-wave origin time discrepancies. Results for the analyzed earthquakes reveal robust constraints on both azimuth and epicentral distance from the fiber, and demonstrate the ability to mitigate DAS-related artifacts associated with broadside sensitivity and reduced coherency. We demonstrated the potential of the approach for real-time earthquake location and showed its performance when only P-wave recordings are available, underscoring the method’s potential for future DAS-based earthquake early warning implementation.

How to cite: Noy, G., Ben Zeev, S., and Lior, I.: Earthquake Location using Back Projection with Distributed Acoustic Sensing with Implications for Earthquake Early Warning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5259, https://doi.org/10.5194/egusphere-egu26-5259, 2026.

EGU26-5259

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We present a physics-based point source earthquake early warning system using distributed acoustic sensing (DAS) data. All core modules of the system are based on physical principles of wave propagation, and models that describe the earthquake source and far-field ground motion. The detection-location algorithm is based on time-domain delay-and-sum beamforming, and the magnitude estimation and ground motion prediction are performed using analytical equations based on the Brune omega squared model. We demonstrate the performance of the system in terms of magnitude estimation and ground motion prediction, and in terms of real-time computational feasibility using local 3.1 ≤ M ≤ 3.6 earthquakes. This DAS early warning system allows for fast deployment, circumventing some calibration phases that require gathering local DAS earthquake data before the system becomes operational.

How to cite: Lior, I. and Ben Zeev, S.: Physics-based earthquake early warning using distributed acoustic sensing, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1594, https://doi.org/10.5194/egusphere-egu26-1594, 2026.

EGU26-1594

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As a vehicle approaches the fiber-optic cable, the distributed acoustic sensing (DAS) records a broadband strain rate, which corresponds to propagating seismic waves at high frequencies (>1Hz) and to quasi-static strain fields at low frequencies (<1Hz). However, characterizing the subsurface media through quasi-static deformations remains challenging. Here, we propose a new method for imaging shallow urban subsurface structures using quasi-static strain waveforms, measured with fiber-optic cables. This technique utilizes the quasi-static waveform of a single DAS channel to generate a local 1D velocity model, thereby enabling high-resolution imaging of the underground using thousands of densely packed channels. We employed the Markov Chain Monte Carlo (MCMC) inversion strategy to investigate the depth range of inversion using car-induced quasi-static waveforms. The synthetic data demonstrates that the quasi-static strain field generated by a standard small car moving over the ground enables detailed imaging of structures at depths from 0 to 10 meters. Additionally, we conducted field experiments to measure the 2D shear-wave velocity model along a highway using quasi-static strain waveforms generated by a four-wheeled small car. The velocity structure we obtained is closely aligned with that derived from the classical surface-wave phase-velocity inversion. This consistency indicates that the inversion depth range is comparable to the simulation results, which confirms the applicability of this method to real data. In the future, we anticipate using the city's extensive fiber-optic communication network to record quasi-static deformations induced by various types of vehicles, thereby enabling imaging of the urban subsurface at a citywide scale. This will provide valuable insights for the design of urban underground infrastructure and for assessing urban hazards and risks.

How to cite: Tang, L., Bertrand, E., Stutzmann, E., Bonilla Hidalgo, L. F., Mohammed, S. A., Gélis, C., Hok, S., Lehujeur, M., Leparoux, D., Gugole, G., and Durand, O.: Quasi-static waveform inversion from DAS observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3915, https://doi.org/10.5194/egusphere-egu26-3915, 2026.

EGU26-3915

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Urban areas are highly vulnerable to the impacts of geohazards due to their dense populations and complex infrastructure, with potentially severe consequences for human life and economic stability. Improving our knowledge of near-surface and shallow subsurface structures in urban environments is therefore essential for effective seismic hazard assessment and risk mitigation. However, conventional geophysical surveys in cities are often limited by logistical constraints, including strong anthropogenic activity, restricted access, legal limitations, and risks associated with instrument deployment. In this context, repurposing existing telecommunication optical fibers (so-called dark fibers) as dense seismic sensing arrays using Distributed Acoustic Sensing (DAS) offers a powerful alternative for urban subsurface investigations. This approach enables continuous, high-resolution seismic monitoring without the need for extensive field instrumentation.

The megacity of Istanbul (Turkey) is located in one of the most tectonically active regions worldwide and is exposed to significant seismic hazard. Since May 2024, we have been continuously recording passive seismic data using Distributed Acoustic Sensing (DAS) along an amphibious fiber-optic cable, is deployed in the urban district of Kartal (eastern region of Istanbul) and immediately offshore. In this study, we focus on the 3 km-long urban segments of the fiber. We analyze ambient seismic noise generated by various anthropogenic sources, such as train and vehicle traffic and other urban activities, and evaluate their suitability for high-frequency, DAS-based passive seismic interferometry in a complex and heterogeneous urban setting.

We develop and adapt processing strategies for ambient-noise interferometry that address the challenges of dense urban environments and DAS array geometries, including the identification of suitable fiber sections, channels, and source-receiver configurations, as well as preprocessing schemes designed for strongly anthropogenic noise.The objective is to retrieve high-resolution, urban-scale subsurface velocity models that improve our understanding of shallow structures and material properties relevant to seismic hazard. Ultimately, this work aims to establish efficient methodologies for imaging the urban subsurface using existing infrastructure, contributing to improved geohazard assessment and supporting sustainable urban development in seismically active regions.

How to cite: Pinzon-Rincon, L., Rodríguez Tribaldos, V., Jordi Gómez Jodar, J., Martínez-Garzón, P., Hillmann, L., Feyiz Kartal, R., Kılıç, T., Bohnhoff, M., and Krawczyk, C.: Urban-Scale Seismic Imaging Using Ambient Noise and Dark Fiber Distributed Acoustic Sensing in Istanbul, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7987, https://doi.org/10.5194/egusphere-egu26-7987, 2026.

EGU26-7987

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Distributed acoustic sensing (DAS) has transformed geophysical, environmental, and infrastructure monitoring. However, the increasing bandwidth and sensitivity of modern interrogators now extend into the audio range, introducing a material privacy risk. Here we demonstrate, through in-situ experiments on live fibre deployments, that human speech, music, and other acoustic signals can be under certain acquisition conditions.

We show that intelligible speech can be accurately recovered and automatically transcribed using neural networks. Experiments were conducted on both linear and spooled fibre geometries, deployed as part of an ongoing geophysical survey. We find that coiled layouts, which are common in access networks (e.g., slack loops or storage spools), exhibit enhanced sensitivity to incident acoustic waves relative to linear layouts. Modelling indicates this arises from increased broadside sensitivity and reduced destructive interference for longer wavelength acoustic fields over the gauge length. We systematically assess how acquisition parameters, such as source-fibre offset, influence signal‑to‑noise ratio, spectral fidelity, and speech intelligibility of recorded audio. We further show that neural network based denoising strategies improves intelligibility and fidelity of recorded audio, thereby exacerbating privacy concerns.

These findings demonstrate that appropriate interrogation of existing fibre infrastructure - including fibre‑to‑the‑premises links, smart-city infrastructure, and research cables – can function as pervasive, passive wide-area acoustic receivers, creating a pathway for inadvertent or malicious eavesdropping. We discuss practical mitigation strategies spanning survey design, interrogation configuration, and data governance, and argue that the incorporation of privacy‑by‑design into deployment and processing is crucial to leverage the unique benefits of DAS while managing emerging ethical and legal risks.

How to cite: Smith, J. L., Lythgoe, K., Curtis, A., Whitelam, H., Seager, D., Johnson, J., and Belal, M.: Privacy Concerns of DAS: Eavesdropping using Neural Network Transcription, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17496, https://doi.org/10.5194/egusphere-egu26-17496, 2026.

EGU26-17496

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