This session invites studies focused on methods and applications for event detection and location using seismic, hydroacoustic, infrasound, and radionuclide technologies. Contributions on the enhancement of seismic and acoustic velocity models, as well as the modeling of acoustic wave propagation, ATM of radionuclides, and contributions regarding the data fusion of various technologies are welcome. The session invites contributions on Nuclear-Test-Ban Monitoring using either IMS or OSI instrumentation, data or methods. This can be either in the context of explosion monitoring of actual or historic events or by taking into account fictitious scenarios like the National Data Centre Preparedness Exercises (NPE).
Contributions to the civil and scientific use of IMS data are encouraged. Civil applications include disaster risk reduction through early warning or hazard assessments for earthquakes, tsunamis, and volcanic activity. Earth science applications encompass analyses on different natural or anthropogenic sources as well as studies on climate change, ocean processes, solid Earth structure, and atmospheric circulation. Finally, contributions on the application of machine learning in event detection, localization, discrimination, and monitoring are highly encouraged.
PICO: Tue, 5 May, 10:45–12:30 | PICO spot 1b
Ocean soundscape analysis frequently relies on time-averaged metrics, treating geophony as a quasi-stationary background component. This approach obscures the stochastic, high-amplitude variability introduced by solid Earth seismicity, which dominates the low-frequency spectrum (<100 Hz) and exerts significant, transient environmental forcing. A fundamental knowledge gap remains regarding the transfer function between seismic ground motion and the resulting hydroacoustic pressure field. While T-phase excitation is known to occur via scattering at rough fluid-solid interfaces, the global scaling relationship between seismic source parameters (magnitude, depth, focal mechanism) and far-field acoustic intensity remains unconstrained. Specifically, it is unknown whether seismic-to-acoustic coupling is a globally constant scalar or a spatially variance function of local boundary conditions.
We present a comprehensive, data-driven analysis of the global earthquake soundscape, utilizing ten years (2015–2025) of continuous hydrophone records from the CTBTO International Monitoring System (Pacific, Atlantic, and Indian Oceans). Integrating IRIS seismic catalogs, we analyze over 10,000 events to quantify T-phase energy flux and duration. To isolate source mechanics from propagation effects, we correct for transmission loss using 3D ocean acoustic models and apply backprojection techniques to verify source azimuths. We employ a machine-learning framework to regress acoustic observations against high-resolution geophysical constraints, including Slab 2.0 geometry, slab thermal structure (controlling attenuation), global sediment thickness maps, and seafloor roughness metrics.
Our results challenge the assumption of a linear magnitude-loudness relationship. We identify significant spatial heterogeneity in T-phase generation, governed by a "Tectonic Efficiency" factor unique to specific margins. We demonstrate that acoustic amplitude and signal duration are strongly modulated by the incidence angle of P- and S-waves relative to the seafloor slope (conversion efficiency) and the scattering potential of the bathymetric interface. Furthermore, we find that thermal structure and sediment cover significantly damp high-frequency injection into the SOFAR channel at specific subduction zones. By resolving the physics of this coupling, we transform earthquake geophony from noise into a deterministic signal. This framework allows for the inversion of far-field hydroacoustic records to monitor changes in seafloor roughness and near-surface crustal properties, providing a novel remote sensing modality for the ocean floor.
How to cite: Olugboji, T., Mittal, T., Swar, S., and Heaney, K.: Spatio-Temporal Variability of the Earthquake-Generated Ocean Soundscape: Decoupling Source Magnitude from Acoustic Conversion Efficiency, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17363, https://doi.org/10.5194/egusphere-egu26-17363, 2026.
Oceanic T-waves are sensitive to weak seismic and acoustic signals and hold significant advantages for constraining earthquake and tsunami characteristics, monitoring ocean temperature changes, and other marine environmental observations. However, the quantitative relationship between T-wave features and seismic source parameters remains unclear. This study analyzes the characteristics (e.g., arrival time, duration, energy) of T-waves excited by the 3 April 2024 Mw 7.3 Hualien, Taiwan mainshock and its aftershock sequence, using records from Pacific CTBTO hydrophone arrays and island-based seismic stations. The results indicate that the Hualien earthquake sequence generated prominent T-wave signals, whose excitation strength correlates positively with earthquake magnitude. Furthermore, systematic differences in energy were observed between T-waves excited by near-shore earthquakes and those from typical submarine earthquakes, suggesting that source location and mechanism play a critical role in T-wave generation efficiency. The analysis confirms that T-waves, even after long-distance propagation, retain high-frequency information from the source process. Their waveform characteristics can provide independent constraints on source parameters, offering valuable insights for utilizing T-waves in source parameter inversion.
How to cite: Zhou, Y., Zhang, Y., Xu, M., Ni, S., and Chu, R.: Characteristics of T-waves Excited by the 3 April 2024 Mw 7.3 Hualien, Taiwan, China Earthquake Sequence and Their Relationship with Source Parameters, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20149, https://doi.org/10.5194/egusphere-egu26-20149, 2026.
The explosive yield- seismic magnitude relation of shallow submarine explosions are not well confined. Local agencies often use local seismic magnitude, such as the traditional richter scale, which are often not calibrated for submarine environments. The importance of an estimated explosive yield in TnT equivalent becomes obvious when security concerns arise. After the North Stream events a number of very differing magnitude were presented by several seismological surveys and therefore the related yield estimates varied a lot. This lead to derived estimates ranging from tens of kg to hundreds of kg TnT equivalent explosive used in the North Stream explosions, giving different plausible scenarios for potential perpetrators.
We present an relatively simple and fast approach to use the comparison of recorded and forward modelled envelope and cepstral information to derive the moment magnitude of several large and small submarine explosion in the Baltic sea. Moment magnitudes are more robust in comparison to local magnitudes. We asses the performance of this approach by relating the moment magnitudes to yield estimates from known explosive events. We use events from the Baltic sea, including events from offshore Bornholm from September 2025 with around 400kg TnT yield, recorded at local and regional distances up to 500km.
Infrasound recordings of stations in Germany are in good correlation with the seismic recordings, showing the possibility of combined energy release estimates. The strong importance of the source depth and shallow submarine geology is highlighted by the modelling results, providing still a large uncertainty range for unknown sources. We do find in general a good agreement between the estimated yield and actual yield for the known sources.
How to cite: Steinberg, A., Weidle, C., Dahl-Jensen, T., and Lund, B.: Explosive yield estimates for shallow water explosions from moment magnitudes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13924, https://doi.org/10.5194/egusphere-egu26-13924, 2026.
A graph of body-wave magnitude (mb) against the logarithm of the announced yield was prepared for a subset of the Soviet peaceful nuclear explosions (PNEs) featured in Sultanov et al. (1999). A magnitude-log(yield) relation was derived using linear regression. Explosions detonated in cavities or near the surface in cratering experiments were not used, so the resulting relation is for confined explosions in competent rock of various types. The mb used was the robust network mb derived by the International Seismological Centre (ISC)’s revised procedures (Bondàr and Storchak 2011). The effect of relocation of some of the epicentres by up to 90 km (difference between ISC revised location and ground truth from Mackey et al. 2017) on network mb values was found to be negligible at one decimal place. The magnitude-log(yield) relation was determined by orthogonal regression, accounting for errors in both mb and yield.
UK Ministry of Defence © Crown Owned Copyright 2026/AWE.
How to cite: Peacock, S.: Magnitude-yield relation for Soviet Peaceful Nuclear Explosions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2533, https://doi.org/10.5194/egusphere-egu26-2533, 2026.
The estimation of seismic moment tensors for shallow sources is known to be highly sensitive to near-source conditions, including surface topography and shallow geological structure, which are often poorly constrained. In this contribution, we present a sensitivity analysis as part of a uncertainty quantification effort, aimed at assessing how uncertainties in near-source parameters propagate into uncertainties in inferred seismic moment tensors.
The study focuses on the Degelen Mountains dataset, which provides a well-documented setting with shallow explosive sources and complex near-surface geology.
Our methodology relies on high-fidelity 3D forward simulations of seismic wave propagation using the spectral element method, allowing accurate modeling of topographic effects and strong near-surface heterogeneities. Uncertainties in geological properties in the immediate vicinity of the source are represented using perturbations from stochastic parameterizations based on a correlation length setting, enabling the generation of physically consistent
realizations of the near-source medium. For each realization, synthetic waveforms are computed and used to perform moment tensor inversions, from which the variability of source parameters is quantified.
This framework allows us to systematically explore the sensitivity of moment tensor solutions to localized uncertainties and to identify the dominant contributors to source-related ambiguity and provide new insights into the robustness and limitations of moment tensor inversion for shallow seismic sources in complex environments.
How to cite: Burgos, G. and Guilllot, L.: Quantifying the impact of near-source uncertainties on seismic moment tensor inference, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17929, https://doi.org/10.5194/egusphere-egu26-17929, 2026.
Mitigating Seismic Ground Vibration (SGV) near the EKA/AS104 array at Eskdalemuir is increasingly important as Scotland expands wind farm development to meet its 2045 Net Zero commitments. Based on concerns about potential impacts on CTBT monitoring, the UK MoD currently restricts wind farm development near the EKA array, based on an empirical seismic forecasting model. This model assumes a single point source and relies on empirical attenuation and seismic velocity models. In 2004, via a student research paper the UK-MoD also set a limit on the maximum rms ground displacement of 0.336 nm for wind farm development within 50km of EKA array. Our results show that background seismic noise has significantly increased in the last 20 years due to the development of commercial forestry and anthropogenic activity.
To provide an evidence based assessment, two independent studies were commissioned . The first deployed surface seismic stations in a linear array up to 10 km from an existing wind farm and measured SGV across wind speeds from 0 to over 20 m/s. The data show that no detectable turbine related background seismic noise beyond approximately 5.0 km, demonstrating that real-world conditions differ substantially from the assumptions in the MoD’s model.
A second study drilled and cased a 200 m borehole near the EKR4 array element and installed a modern broadband seismometer, along with two additional sensors at the wellhead for comparison. It is well known that borehole sensors—already standard at many CTBT stations—significantly reduce SGV noise and improves signal quality. Data collected throughout 2025 show reductions of ~10 dB on calm days, and up to 25 dB on windy days within the MoD bandwidth of interest (2 to 8 Hz). The borehole sensor shows a clear improvement in signal-to-noise ratios, resulting in clear P-wave arrivals for teleseismic events. Importantly, the study also found that the original MoD threshold of 0.336 nm limit is routinely exceeded due to forestry activities and other man-made sources.
Thus, these findings demonstrate that wind farms have minimal seismic impact beyond ~5 km of such wind farm and that borehole sensors can substantially enhance the array’s resilience to environmental noise. This evidence supports revising the current MoD moratorium to allow unrestricted wind farm development at distances of not less than ~5 km from the Array. The wind industry has offered to drill and install borehole seismic sensors to supplement EKA elements, further strengthening the array’s capability to detect clandestine nuclear tests in support of the CTBT and reducing SGV from other anthropogenic sources, ensuring the long-term operational integrity of the array.
How to cite: Hasting, M. and Suárez, G.: Evidence-Based Seismic Impact of Wind Farms and Borehole Sensor Performance at the EKA Array, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7897, https://doi.org/10.5194/egusphere-egu26-7897, 2026.
Through a cooperation between Korea Institute of Geoscience and Mineral Resources (KIGAM) and Institute of Astronomy and Geophysics (IAG), a seismo-acoustic array was installed in Umnugovi area of the southern Govi, Mongolia in September, 2025 for studying regional earthquakes. The study area experienced two big magnitude earthquakes in 1903 and 1960. The magnitude of the former event was 7.5 and the later one was 7.0. Since the 1903 event occurred, lots of small and middle magnitude events have struck the area but the calculation for attaining precise information of seismic parameters such as epicenter, depth of event, origin time, magnitude was partially limited due to poor seismic network in the area. As an initial step to constrain the solutions for the parameters, a single array process is applied with a seismo-acoustic array named HEXAR which is composed of 10 seismometers, 4 Chaparral M21 acoustic sensors, and hose arrays for reducing background wind noise. HEXAR consists of a relatively large array of 2 km aperture as a hexagonal shape and a small seismo-acoustic array of 0.5 km-aperture inner triangular shape. The Progressive Multi-Channel Correlation (PMCC) method is used for the detection and analysis of regional earthquakes and artificial events. For a preliminary stage of the analysis, separating artificial events from natural earthquakes is processed with a discriminant utilizing short period Rayleigh wave and infrasound signal. In this study, clear features of man-made events from two mines in Umnugovi area is presented with the analysis on the detected Rg phase, infrasound signal and epicenter.
How to cite: Kim, T. S.: An analysis on the artificial events in Umnugovi area, Mongolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8756, https://doi.org/10.5194/egusphere-egu26-8756, 2026.
A combined analysis of seismic and acoustic signal observations for tracking explosive sources generated by the bombardment and shelling during the Russia-Ukraine conflict is presented. Events reported in the bulletins provided by IDC/CTBTO are used to identifying and associating detections of stations of the Central east European Infrsound Network (CEEIN). Seismo-acoustic signature (signal shape and amplitude, frequency content), as well as the propagation path of infrasonic signals, were analysed. As direction and speed of stratospheric winds are subject to change with time, selected events were analysed regarding their yield equivalents under various atmospheric conditions. By using infraGA 2D ray tracer through NRL-G2S atmospheric model, stratospheric and thermosphere infrasonic phases were identified and the energy release, which is described by the equivalent of TNT yield, is estimated by the empirical scaling of Los Alamos National Laboratory, published by Whitaker et al. (2003).
How to cite: Mitterbauer, U. and Ghica, D.: Assessment of yield equivalents from seismo-acoustic records under various atmospheric conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9736, https://doi.org/10.5194/egusphere-egu26-9736, 2026.
According to the Global Volcanism Program (GVP) of the Smithsonian Institution 1,281 volcanoes are currently considered potentially active, although only a small fraction is monitored in real time. For distant or inaccessible volcanoes, remote monitoring techniques are the only effective mean for continuous observation.
This study assesses the effectiveness of remote detection of explosive volcanic activity through infrasound observations between 2011 and 2020. A detection algorithm has been developed and applied to eruptions recorded in the GVP database with a Volcanic Explosivity Index (VEI) ≥ 3. The analysis has used data collected from 43 infrasound stations of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) International Monitoring System (IMS) worldwide network, with distances up to 4,500 km from the selected volcanoes.
The approach has combined event compilation, infrasound data processing and spatio-temporal correlation analysis to associate detections with explosive volcanic activity. The algorithm has been developed based on the Progressive Multi-Channel Correlation (PMCC) method, integrated with the atmospheric profile calculated at the time of each event: this has been realized by incorporating meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF) models ERA-Interim and ERA5 and the Ground-to-Space (G2S) empirical model.
Validation with event reports from the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) International Data Centre (IDC) has demonstrated the robustness of the method. The algorithm has successfully identified 50 of the 67 eruptions and 128 of the 186 distinct explosive events (with VEI ≥ 3) at 30 volcanoes, representing detection efficiencies of 75% and 69%, respectively.
The results highlight that the described method, joint to the IMS global infrasound network capability of provide a reliable tool for remote monitoring of explosive volcanic activities: this, enhances the global early warning potential, in particular in remote areas where local monitoring networks are not available.
How to cite: Matos, S., Campus, P., Ripepe, M., and Wallenstein, N.: Detection of Explosive Volcanic Activity through Infrasound: A Global Assessment Using the IMS Network (2011–2020), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13766, https://doi.org/10.5194/egusphere-egu26-13766, 2026.
Seasonal variability in source activity and atmospheric temperature were retrieved from 11 years of infrasonic ambient noise. Variable lag times between an array (IMS array I53US) and single microbarometer (POKR, AK) were obtained from envelopes of cross-correlation functions. Beamforming and one-bit normalization significantly enhanced the stationary phase. Both microbaroms and surf appeared abundantly present, in the 0.1 to 2.0 Hz frequency band. Modeling revealed both tropospheric and stratospheric propagation of the infrasound, following traditional and more unconventional propagation mechanisms. Virtual source-receiver refractions from stratospheric altitudes appeared a plausible explanation for the unusual short lag times, which allows for new ways to passively probe the stratosphere.
Keypoints:
- The cross correlation of infrasonic ambient revealed coherent energy from microbaroms and surf from a broad-band analysis
- Seasonal variability was retrieved in source and medium variations in 11 years of microbarometer data
- Stratospheric virtual source-receiver refractions can explain the unusual short lag times, providing new means to probe the upper atmosphere
How to cite: Evers, L. G., Assink, J. D., and Fricke, J. T.: Evidence for virtual source-receiver refractions in cross correlations of infrasonic ambient noise, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2319, https://doi.org/10.5194/egusphere-egu26-2319, 2026.
This study focuses on the infrasound observation and case-based event analysis of recent and exceptional rocket launches for and reentries from space missions. Highlight cases of powerful launches and remarkable reentries are:
- NASA’s Artemis 1 maiden flight in 2022 (and probably Artemis 2 in early 2026)
- SpaceX’s Starship flight tests 1 to 11 from 2023 to 2025 (and probably Starship 12 in early 2026)
- ESA’s Ariane 6 maiden flight in 2024 (and further launches in 2025+)
- Blue Origin’s New Glenn maiden flight in 2025 (and further launches in 2025+)
- Selected and detected reentries from Starship, New Glenn and Falcon 9 rockets
Rocket launches and reentries are powerful atmospheric noise sources detectable at infrasound arrays in hundreds to thousands of kilometers distance. Recorded signatures originate from the ignition, launch, supersonic movement, stage separation and reentry of rockets within the first about 100 kilometers of altitude of the atmosphere. Using microbarometer arrays of national observation networks and the International Monitoring System for the Comprehensive Nuclear-Test-Ban Treaty, such infrasound events can be remotely identified, localized and characterized.
How to cite: Pilger, C. and Hupe, P.: Infrasound detection highlights of rockets from and to space, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4824, https://doi.org/10.5194/egusphere-egu26-4824, 2026.
The OSIRIS-REx sample return capsule re-entry provided a unique, controlled opportunity to study atmospheric shock wave propagation from a high-altitude source. Unlike natural meteoroids, which often undergo complex fragmentation and ablation, the capsule offered a stable source for characterizing specific acoustic generation mechanisms. We utilize infrasound data recorded by a regional network of ground-based sensors to analyze the acoustic signature associated with the descent. This study employs a semi-analytical weak-shock approach developed for a cylindrical line source to evaluate signal evolution as the wavefront propagates through the atmosphere. We examine the applicability of established shock theories to the recorded data, comparing theoretical predictions with the observed waveforms. The analysis explores the relationship between source characteristics and observations, providing a framework for better understanding the physics of non-fragmenting and non-ablating entries. These findings have broader implications for the monitoring and characterization of space debris, artificial re-entries, and meteoroids using infrasound stations.
SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. Cleared for release.
How to cite: Silber, E. and Sawal, V.: Weak-shock analysis of the acoustic signals generated by the OSIRIS-REx re-entry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2618, https://doi.org/10.5194/egusphere-egu26-2618, 2026.
A network of radionuclide stations forms one part of the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). These radionuclide stations are highly sensitive and continuously monitor the atmosphere for tiny traces of radioactive fission and activation products. All IMS radionuclide stations have a high-volume sampler for detecting particulate radionuclides; some are also equipped with noble gas systems for measuring radioxenon. Specific radioactive xenon isotopes are more likely to escape from underground nuclear explosions and exhibit less complex atmospheric transport characteristics.
A central challenge of radioxenon monitoring for the CTBT is attributing and classifying detections originating from reactor sources. As was seen in the aftermath of the announced North Korean nuclear test explosions, atmospheric transport modelling is crucial for interpreting the spatial and temporal relevance of radioxenon detections in the context of potential CTBT non-compliance.
In this respect, the IMS noble gas system at RN38 in Takasaki, Japan, is very important due to its location downwind of the Korean Peninsula, particularly during the northern winter months. In summer, the influence of the East Asian monsoon leads to dynamic patterns that extend further north and north-east.
Several episodes of considerably high radioxenon activity concentrations in the range of tens of mBq/m³ were observed at RN38 in the years 2024 and 2025. These activity concentrations are ten to twenty times higher than those usually observed at comparable stations, but are still several orders of magnitude below levels of radiological concern. Backward atmospheric transport modelling investigates the potential source region of these detections by identifying areas of coincident atmospheric sensitivity. This enables a clear attribution to a common source region around Yongbyon. In particular, the North Korean nuclear test site can be excluded as the origin of the recurring detections. However, the potential blinding effect for telltale traces from nuclear tests, as well as their impact on other monitoring stations in the region and the IMS, is estimated by evaluation of forward ATM forecasts for hypothetical emissions from the North Korean test-site.
How to cite: Ross, J. O., Brander, S., and Hupe, P.: Coincidence source localization by backward atmospheric transport modelling for a series of radioxenon detections at the IMS station RN 38, Takasaki, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21180, https://doi.org/10.5194/egusphere-egu26-21180, 2026.
