Orals: Thu, 7 May, 08:30–10:15 | Room 1.15/16
Detecting ionospheric electric field anomalies that precede earthquakes is still an open scientific challenge. Progress is delayed by limitations in current observational methods and the lack of standardised, reproducible analysis and approaches. As a result, reported pre-seismic signatures often remain inconsistent and hard to validate across different events and datasets.
This study presents a data-driven deep learning (DL) approach that moves beyond traditional model-based frameworks by utilizing satellite based ionospheric electric field measurements from the DEMETER mission (2005 - 2010). A grid based geospatial organization is applied to ensure consistent spatial mapping of the observed spectral electric field data, resulting in structured time series for analysis. The methodology focuses on lower frequency bands below 3 kHz, comprising calibrated data from 11 distinct frequency bands. The study adopts an iterative rolling-window strategy instead of the conventional fixed division of data into training and validation sets, with background corrections applied iteratively within each window. An unsupervised LSTM autoencoder is implemented and trained using this approach, preserving long term temporal nature of data. Anomalies detected by the model are subsequently examined for potential seismic associations and evaluated using statistical tests. A statistical investigation on spatial and temporal windows identifies an optimal configuration of a 22° x 22° spatial window along the orbital foot print, and a 48-hour temporal window for the study. Under this configuration, models trained solely on non-seismic data are able to detect anomalous sequences that show a statistically significant association with seismic events, exceeding the random baseline with a 2 - 3σ deviation range.
This study shows that modern deep learning methods, combined with flexible and adaptive training strategies and sound statistical analysis, can successfully extract useful information from satellite-based ionospheric electric-field data.
How to cite: Babu, M.: Deep Learning Model for Detecting Global Ionospheric Electric Field Perturbations and Seismic Correlation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21822, https://doi.org/10.5194/egusphere-egu26-21822, 2026.
This study examines the seismic sequence, which stroke the Central Italy in 2016, focusing on the relationship between static displacement fields and induced atmospheric perturbations in terms of Acoustic Gravity Waves (AGWs). Specifically, we investigated the three events of the sequence occurred on August 24th, October 26th and October 30th. Displacement fields for the main earthquakes were modeled using the Okada approach and validated with Global Navigation Satellite System (GNSS) data, providing strong geodetic constraints. AGW activity was assessed through potential energy derived from ERA-5 temperature profiles. For the August 24th earthquake (Mw 6.1, EQ1), the observed AGW was well reproduced by the Magnetosphere Ionosphere Lithosphere Coupling (MILC) model confirming the direct connection between seismic event and atmospheric temperature perturbations. The October 26th earthquake (Mw 5.9, EQ2) showed no AGW injection, consistent with model predictions. During the October 30th event (Mw 6.5, EQ3), the presence of adverse meteorological events inhibited any detection of potential seismic-induced AGW signals. These findings highlight that also moderate-to-strong earthquakes might generate propagating AGWs which are crucial for reliable earthquake precursor identification.
How to cite: Falanga, M., Cusano, P., D'Angelo, G., De Lauro, E., Lepreti, F., and Piersanti, M.: From Fault Ruptures to Atmospheric Perturbations: Examining the 2016 Norcia Seismic Sequence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3100, https://doi.org/10.5194/egusphere-egu26-3100, 2026.
Solar activity and its sharp variability generally produce large-scale disturbances in Earth’s magnetosphere, inducing geomagnetic fluctuations that can be measured globally through ground-based magnetometers and Low Earth Orbit (LEO) satellite observations. These disturbances, driven primarily by solar wind variability and coronal mass ejections, may cause geomagnetic storms and induce electrical currents in Earth’s ionosphere and crust, leading to measurable electromagnetic signatures. Considering that both tectonic deformation and geomagnetic variations affect the physical state of Earth’s lithosphere (even though with different weights), possible links between solar-driven geomagnetic activity and seismic processes have been proposed in the literature.
Preliminary analyses indicated that while geomagnetic storms produce large and well-defined electromagnetic perturbations in the Earth–ionosphere system and well-recorded by geomagnetic ground magnetometers, any corresponding modulation of seismicity is subtle and difficult to distinguish from background tectonic variability. Nonetheless, localised correlations in highly conductive, fluid-rich fault systems suggest that electromagnetic effects may contribute to earthquake timing in specific geological settings when faults are near the critical failure due to accumulated tectonic stress. Over the past several decades, a number of hypotheses have proposed that such geomagnetic disturbances could influence the timing of earthquake occurrence by modulating crustal stress, pore-fluid pressure, or electrochemical processes along active faults.
This contribution emerged from the International Space Science Institute (ISSI) Team 23-583 (57) meeting activities, which proposed a new hypothesis of geomagnetic–seismic coupling where geomagnetic fluctuations generate electric currents within the conductive layers of the lithosphere. The hypothesis consists of electrolytic deposition of elements on fault surfaces due to telluric currents acting in lithospheric fluids, capable of weakening the cohesion between foot and hanging walls and consequently inducing slippage. Such a hypothesis is compared with others, including (1) Lorentz-force interactions between induced telluric currents and crustal rock masses, (2) electromagnetic triggering of electrokinetic fluid migration in fault zones, and (3) magnetoelastic effects in stressed, magnetically susceptible rocks.
Acknowledgment
We acknowledge ISSI (Bern) /ISSI-BJ (Beijing) for supporting the International Team 23-583 (57) “Investigation of the Lithosphere Atmosphere Ionosphere Coupling (LAIC) Mechanism before the Natural Hazards” led by Dedalo Marchetti and Essam Ghamry, and in particular, Prof. Dimitar Ouzounov for fruitful scientific discussions.
How to cite: Fidani, C. and Marchetti, D.: Interaction mechanism of electric current induced by solar activity and earthquake faults, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20657, https://doi.org/10.5194/egusphere-egu26-20657, 2026.
In this work we plan to study local deviations from Solid Earth Tides (L-SET) adopted by the IERS-2010 model. The study is performed exploiting the coordinates of about 100 stations worldwide estimated by GNSS technique. The coordinates solutions, expressed both in XYZ and local NEU, is achieved over a time series 20 years long at least and with a sampling rate in turn of 1 day (1D) and 3 hours (3H). The computations were performed in Precise Post Processing mode (PPP), switching off the IERS-2010 tides model. In practice, the study consists of estimating the Love and Shida numbers of (L-S) SET, station by station. The 1D were used to estimate L-S of long periodic tides: 18.6, half-year, monthly 13.6 and 13.3 days; while 3H data were helpful for diurnal and semi-durnal tides. The L-S estimation is done using two different numerical approaches: the nonlinear Levenberg-Marquardt least squares and the Gradient Descent and the Gauss-Newton algorithms. This investigation is proving to be particularly compelling because, since L-S define the level of rigidity of the Earth layers. For these reasons they could be deemed as potential seismic precursors. The comparison between the two types of approaches needs to understand what is the more reliable numerical approach in terms or robustness and solution stability.
How to cite: Vespe, F., Miglionico, R., and Parisi, K.: On the application of non-linear optimization algorithms for an advanced estimation of Local Solid Earth Tides (LSET) by GNSS solutions to be used as possible precursors of seismic events , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6010, https://doi.org/10.5194/egusphere-egu26-6010, 2026.
The total electron content (TEC) of the global ionosphere map (GIM) is used to study seismo-ionospheric precursors (SIPs) of the 29 July 2025 Mw 8.8 Kamchatka earthquake. Statistical analyses show that SIPs of GIM TEC significantly frequently decrease specifically over the epicenter area on day 21-26 and 1 before the earthquake. The distance between northern and southern crests of equatorial ionization anomaly in GIM TEC as well as downward ion velocities measured by advanced ionospheric probe (AIP) onboard FORMOSAT-5 (F5) satellite are used to estimate electric fields associated with the observed SIPs. Results show that the seismo-electric fields related the two SIPs estimated by the GIM TEC and F5/AIP ion velocity are about 1 mV/m westward. Meanwhile, TEC derived by more than 1,400 ground-based GNSS receiving stations in Japan and Taiwan is employed to examine the spatiotemporal evolution of seismic- and tsunami-traveling ionospheric disturbances (STIDs and TTIDs). A normalized process applied to GNSS TEC clearly shows STIDs and TTIDs traveling with the horizontal speeds of 3.6 km/s and 273.2-215.4 m/s, respectively. The estimated TTID source is located within about 90 km of the center of the main slip area.
How to cite: Liu, J.-Y., Wen, Y.-C., Chang, F.-Y., Wu, T.-Y., Chen, Y.-I., Song, R., Hattori, K., Huang, C.-Y., and Satake, K.: Total electron content variations related to seismo-ionospheric precursors and seismic/tsunami waves triggered by the 29 July 2025 Mw 8.8 Kamchatka Earthquake, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17020, https://doi.org/10.5194/egusphere-egu26-17020, 2026.
Despite advances in satellite remote sensing, predicting large earthquakes remains a major challenge. Building on previous DEMETER observations of seismo-ionospheric disturbances (e.g., Němec et al., GRL, 2008), we investigate atmospheric and space-electrical variations as potential ionospheric earthquake precursors, with an emphasis on the D region. Such observations can improve our understanding of lithosphere–atmosphere–ionosphere coupling and support the development of short-term prediction approaches.
We present the PRELUDE CubeSat mission (Precursory electric field observation CubeSat Demonstrator), dedicated to detecting earthquake-related ionospheric signatures and clarifying their physical mechanisms. PRELUDE is scheduled for launch in Japanese Fiscal Year 2025 within JAXA’s 4th Innovative Satellite Technology Demonstration Program, on Rocket Lab’s Electron from New Zealand (Mahia Peninsula, Launch Complex 1). PRELUDE is a 6U CubeSat (8 kg) optimized for VLF electromagnetic-wave intensity measurements. To reduce onboard storage and downlink load, PRELUDE implements an event-focused “drive-recorder” concept that selectively downlinks data acquired around target earthquakes and their vicinity. A key payload innovation is a compact hybrid sensor that combines a Langmuir probe and an electric-field probe—functions typically flown on >100 kg-class satellites such as DEMETER—into a CubeSat-compatible unit. The sensor deploys two booms extending 1.5 m in opposite directions from the spacecraft body via a folding deployment mechanism, enabling plasma and electric-field measurements within CubeSat resource constraints.
This presentation highlights early operational (initial in-orbit) results from PRELUDE and discusses their implications in a multi-satellite context. After DEMETER (local time ~10:30), complementary observations are provided by the China–Italy CSES-1 (local time ~14:00) and CSES-2 (local time ~14:00, with an ~180° orbital phase offset relative to CSES-1), which are in operation in 2026. PRELUDE provides observations at local time ~15:30 and operates during the same period. Coordinated analyses among DEMETER, CSES-1/2, and PRELUDE enable multi-local-time sampling, offering a timely pathway to test local-time dependence of precursor candidates and to better constrain the underlying physical processes.
How to cite: Kamogawa, M., Yamazaki, M., Sone, N., and Development Team, T. P.: PRELUDE CubeSat mission: early operational results and multi-satellite perspectives on ionospheric earthquake precursors, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16132, https://doi.org/10.5194/egusphere-egu26-16132, 2026.
The evolution of phenomena at the interface between the terrestrial surface and the atmospheric boundary layer, like the coupling between litospheric and atmospheric phenomena during an earthquake, can be described as a nonlinear process, affected by mechanically induced disturbances originating from the solid Earth. In this work, a two-dimensional Direct Numerical Simulation (DNS) model is designed to investigate the nonlinear atmospheric response to seismic-wave-induced forcing within the lowest ~100 m of the atmosphere.
The model is based on the incompressible Navier–Stokes equations under the Boussinesq approximation. Stratification is imposed via a prescribed, constant, background buoyancy gradient representative of near-surface stable atmospheric conditions. Seismic forcing is introduced as a dynamical perturbation on the gravity acceleration field.
A set of numerical experiments has been performed to explore the nonlinear dynamics arising from the interaction between stratification, gravity forcing, and intrinsic flow instabilities. Simulations span a range of Reynolds numbers representative of the atmospheric boundary layer, enabling the investigation of transitions from linear wave dynamics to strongly nonlinear flow regimes. These first simulations demonstrate the feasibility of using a reduced-dimensional DNS framework to investigate atmosphere–solid Earth coupling processes at small scales.
The results show the excitation and upward propagation of internal gravity waves, their nonlinear interaction with background shear, and the development of localized instabilities and turbulence. Energy diagnostics highlight anisotropic and scale-dependent transfers, as well as the conversion between kinetic and potential energy driven by the imposed seismic perturbation.
The model provides a controlled platform for studying nonlinear wave–boundary layer interactions and for assessing the potential role of seismic forcing in modulating near-surface atmospheric dynamics.
This study was carried out within the Space It Up project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0 - CUP n. I53D24000060005.
How to cite: Ciardullo, G., Primavera, L., Carbone, F., Gencarelli, C. N., Malara, F., and Lepreti, F.: Nonlinear Response of the Seismic Forcing on the atmospheric Boundary Layer: a 2D DNS Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13267, https://doi.org/10.5194/egusphere-egu26-13267, 2026.
This study presents a multi-instrument investigation of Rayleigh wave–induced ionospheric disturbances following the 29 July 2025 Kamchatka earthquake, with a focus on the mid-field region over the Japanese sector. To investigate the Co-Seismic Ionospheric Disturbances (CSIDs), we used observations from the Japanese GNSS receiver network, GEONET. To obtain the seismic wave-propagation parameters, the vertical component of the F-net seismic waveforms is used. Further, we perform ray tracing of the Rayleigh wave-induced acoustic waves to simulate their upward propagation in the atmosphere/ionosphere, considering the altitude variation of atmospheric temperature and composition. To further corroborate the manifestation of these disturbances in the ionosphere, ionosonde observations from four ionosonde stations, namely Wakkanai (WK), Kokubunji (TO), Yamagawa (TG), and Okinawa (OK), are used to analyse the Multi-Cusp (MC) structures in the lower F-region of the ionosphere. To complement our observation, further synthetic ionogram simulations are performed for all stations, using the propagation characteristics of Rayleigh wave-induced acoustic perturbations that cause plasma density perturbations in the ionosphere, giving rise to the structured MC signatures in the bottom F-region. Combining the observations and simulations, this study provides a comprehensive picture of the ionospheric perturbations caused by strong earthquake-generated Rayleigh waves in the mid-field region.
How to cite: Barad, R. K., Astafyeva, E., Ouar, I. D., and Maréchal, C.: Multi-instrument investigation of Rayleigh wave–induced ionospheric perturbations over Japan following the 29 July 2025 Kamchatka earthquake, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19006, https://doi.org/10.5194/egusphere-egu26-19006, 2026.
Strong seismic events are able to generate atmospheric waves which can propagate in the atmosphere up to the ionosphere and magnetosphere, producing fluctuations of the ionospheric plasma density, as well as variations of the resonance frequency of magnetospheric field lines. The interest in these physical phenomena has significantly increased during the last years, especially thanks to the rapid progresses in the observations of co-seismic signals in the atmosphere, ionosphere, and magnetosphere, made possible by the growing availability of high quality measurements and data provided by Earth and space instruments, and also by reanalysis datasets. In this contribution, we discuss the generation and propagation in the atmosphere of perturbations due to strong seismic events. To this aim, different fluid models are used, in which earthquakes can be described through suitable time profiles which include the main features of real seismic signals. The excitation and vertical propagation of non vanishing modes is investigated for different configuration of the models.
This study was carried out within the “Space It Up” project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0 - CUP n. I53D24000060005.
How to cite: Lepreti, F., Carbone, F., Ciardullo, G., D'Alessi, L., Gencarelli, C. N., and Primavera, L.: Fluid models of atmospheric disturbances generated by strong seismic events, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19521, https://doi.org/10.5194/egusphere-egu26-19521, 2026.
Posters on site: Thu, 7 May, 10:45–12:30 | Hall X3
The first studies on seismic precursors in Italy date back to seventies. At that time in-situ geotechnical measurements were carried out and the data provided by a tiltmeter located near a large dam in North-eastern Italy revealed the appearance of an anomalous movement in one direction till the occurrence near the dam of the destructive (M=6.5) Friuli earthquake on May 06, 1976. This movement was considered a long-term precursor of the earthquake. From then on, systematic research on the seismic precursors started and one of the first multi parametric network was created gradually in the most seismically active area of Central Italy. The parameters sampled and studied were: 1) micromovements (continuously), 2) Radon content in groundwater (sampled every 10/15 days), 3) flow rate of springs (measured every 19/15 days), 4) deep-resistivity (measured every 10/15 days), 5) electric, magnetic and acoustic emission from ground (continuously), 6) intensity of LF (150-300KHz) radio-signals (continuously). During many years of observations several earthquakes precursors were revealed. In eighties, a cooperation among researchers of Italy, Georgia and Kamchatka started; in this framework the content of ions and gases in the water of deep wells located in those regions, collected for 20 and more years, was analyzed. In 1994 a cooperation between Italian and Japanese researchers started for studying possible disturbances in the propagation of VLF (20-80KHz) radio signals and radio receivers were put into operation in Japan and in Italy. In both the mentioned cases, earthquakes precursors were revealed. In 2009 a European Network (INFREP) for studying the disturbances in VLF-LF radio signals in Mediterranean area was set up. Nine receivers were put into operation in Italy, Greece, Crete, Cyprus, Romania, Turkey, Austria and Serbia and once again several earthquakes precursors were revealed. The Italian multiparametric network was closed at beginning of 2000 leaving to the scientific community the lesson that the way to reveal seismic precursors is the merging of data collected by a multiparametric network. Currently, the INFREP network is still in operation even if faced to maintenance problem due to the aging of receivers. On the basis of the results obtained in Italy and in the word in the last fifty years the forecast of some strong earthquake could be possible if multi parametric networks are deployed and maintained in order to regularly collect and analyze the data. The aim of this presentation is to provide a survey of consolidated results on seismic precursors obtained by different research groups and provide a road map for an operational detection of seismic precursors in the seismic prone areas.
How to cite: Biagi, P. F., Ermini, A., and Nico, G.: Fifty years of research on earthquakes precursors: lesson learnt and ways forward, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-158, https://doi.org/10.5194/egusphere-egu26-158, 2026.
At the end of January 2020 an intense seismic crisis occurred on Dodecanese islands. The main earthquakes (Mw= 5.6 and Mw= 5.7) happened on January 30. This seismic activity was studied using the receivers of the INFREP network. Pre-seismic anomalies on the three VLF radio signals (19.58, 20.27, 23.40 kHz) collected by the Cyprus receiver and crossing the zone of the seismic activity were identified. The analysis of daily day/night trend of these signals pointed out a clear anomaly during the night of 29 January 2020, one day before the occurrence of the main shocks of the seismic crisis.
In this work we present a methodology to include the anomalies detected in the VLF radio signals into the epidemic-type aftershock sequence (ETAS) model to establish seismic correlations. The ETAS model is characterized as a self-exciting point process where each seismic event has the potential to trigger subsequent offspring events. Recognized as a benchmark method for Operational Earthquake Forecasting (OEF), it utilizes earthquake catalogues to compute the conditional intensity function, λ(x,y,t), representing the total seismicity rate. To incorporate electromagnetic precursors, our methodology modifies λ(x,y,t) by applying a multiplicative weighting factor, w(x,y,t). This factor reflects the occurrence time and location of VLF anomalies, where the spatial extent of influence is constrained by the Dobrovolsky region.
The proposed methodology builds on previous studies regarding VLF anomalies and the ETAS framework, and could provide a step forward in the operational use of VLF anomalies as seismic precursors. Therefore, we present the first results of the proposed methodlogy to model and simulate earthquake occurrence for the Dodecanese earthquake sequence.
How to cite: Ermini, A., Gioia, D., Parisi, K., Miglionico, R., Hsieh, M.-C., Nico, G., and Yang, Y.-C.: Merging Vlf/Lf data in the epidemic-type aftershock sequence (etas) model: a newperspective operational tool to provide seismic precursors, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22370, https://doi.org/10.5194/egusphere-egu26-22370, 2026.
In this work we study the properties of ionospheric magnetic field and electron density acquired by ESA’s Swarm satellites over the Mediterranean region to identify correlations with the occurrence of strong earthquakes (magnitude M > 5) as part of an earthquake swarm. Precursor anomalies in spatial and temporal distributions of magnetic field and electron density are possibly related to the
pre-seismic electromagnetic (EM) waves, triggered by large earthquakes, that propagate from the lithosphere to the ionosphere above the epicenter region. Such waves disturb a huge ionospheric space area considered to be equal to the earthquake (EQ) preparation zone, derived from the so-called Dobrovolsky’s relationship, with a radius (Rdb) equal to Rdb=100.43M, where Rdb is expressed in km and M is the magnitude of the earthquake. We focus our analysis of Swarm data to the case of earthquake sequence occurred in the Dodecanese islands area, Greece, in January and February 2025. In addition, we study electromagnetic precursors based on the use of low frequency (LF, f = 30-300 kHz) and very low frequency (VLF, f = 3-30 kHz) radio transmitter signals detected by ground-based stations localized in the southern part of Europe, principally in Italy, Greece, Serbian, Romania, and Austria.
How to cite: Nico, G., Eichelberger, H. U., Khan, M. A., and Boudjada, M. Y.: Analysis of Swarm data recorded in January and February 2025 over the Mediterranean region: Case study of Dodecanese earthquake sequence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4269, https://doi.org/10.5194/egusphere-egu26-4269, 2026.
A web platform for the distribution and visualization of VLF/LF data collected by ground-based sensors is presented. The web platform is intended to be used by the scientific community working on the study on anomalies in the propagation of VLF/LF signals in the atmosphere. Users can freely access the platform upon registration and contribute to the analysis of VLF/LF signals. A forum section is designed for discussions and interactions among users about the analysis of VLF/LF signals. Users are allowed to upload the data collected by their VLF/LF sensors after certification of data quality, besides downloading VLF/LF data from the platform.
A Virtual Private Server (VPS) is used to protect again potential breaches and unauthorized access to data. Users can select the location of VLF/LF transmitters and receivers, as well as the time window, and visualize the time series of signal amplitude (and phase if available).
Users can analyze the VLF/LF signals in terms of their wavelet spectrum. In addition, a few algorithmic tools are provided for the automatic detection of anomalies in the time domain. In this work we focus on a new algorithm which has been implemented, based on the Knorr algorithm which is more suitable for the analysis of multidimensional datasets with respect to statistics-based algorithms which require the knowledge of data statistical distribution.
The Knorr algorithm works as follows: given a data sample O in the time series T, it classified as outlier if a fraction p of data samples in T have a distance from O greater than a threshold D. Three types of outliers are defined:
- Global Outlier: the whole dataset is analyzed; this approach is more suitable for the off-line analysis of VLF/LF data;
- Left Outlier: samples already transmitted are analyzed; this approach is useful to detect anomalies in near-real time, with respect to the observed “normal” behavior of the time series;
- Right Outlier: samples transmitted after the occurrence of the anomaly are analyzed; this approach requires an off-line analysis of VLF-LF data and it provides the information about anomalies that have no longer been observed, within a given time window.
How to cite: Parisi, K., Parisi, A., Miglionico, R., and Biagi, P. F.: Study of VLF/LF propagation anomalies in atmosphere by a network of ground-based sensors: a WEB platform for data distribution, analysis and visualization, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8192, https://doi.org/10.5194/egusphere-egu26-8192, 2026.
Perturbations in the electric properties of the ionosphere are observed in correspondence of solar activity (solar wind-magnetosphere-ionosphere coupling) and tectonic activity (litosphere-atmosphere-ionosphere coupling). In this work, we focus on the connection between seismic activity and ionospheric perturbation relevant for definition of electromagnetic seismic precursors observed using electric and/or magnetic measurements collected by ground-based and spaceborne sensors.
We provide a survey of some mathematical models of earthquake precursors in the ionosphere. A quantitative approach is based on the modelling of oscillations of pressure and/or density in the troposphere, acoustic gravity waves induced by earthquake activity. Another approach is based on the electromagnetic modelling of the atmosphere to explain the observed anomalies of the electric and magnetic fields, as well as of the electron content. We discuss a few approximation of the Maxwell’s equations as the on in the range of low frequencies, e.g. the VLF signals used in many studies on seismic precursors. We also discuss the inverse problem of estimating the spatial distribution of subsurface electric charges, induced by the tectonic movement and rock friction in the earthquake preparatory phase, which can explain the measured electric and/or magnetic anomalies observed before earthquakes. Numerical methods are described and results presented.
How to cite: Esposito, A., Miglionico, R., Parisi, K., Oikonomou, C., and Nichidi, E.: A survey of mathematical models for electromagnetic earthquake precursors in the ionosphere: numerical results, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23104, https://doi.org/10.5194/egusphere-egu26-23104, 2026.
Strong natural hazards (NHs) have large social, economic and environmental impacts in several ways. Remote detection and classification of events is therefore an important task. In this study we investigate electric field variations in the sub-ionospheric waveguide between very low frequency/low frequency (VLF/LF) transmitters and the International Network for Frontier Research on Earthquake Precursors (INFREP) receiver facilities. The combined VLF/LF data sets enable to disentangle NH events from local, site-specific influences. Parallel to this long-term multi-station network in Europe we use complementary data sets, among them ionospheric satellite magnetic field measurements from ESA’s Swarm mission.
We show the status of the INFREP network, discuss detection thresholds of the system related to NH events, and improvement potentials with the focus on different data processing methods.
How to cite: Eichelberger, H. U., Nina, A., Kolarski, A., Veselinović, N., Galopeau, P. H. M., Moldovan, I.-A., Nico, G., Besser, B. P., Stachel, M., and Boudjada, M. Y.: Electric field variations in the sub-ionospheric VLF/LF waveguide examined with a distributed receiver network, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22915, https://doi.org/10.5194/egusphere-egu26-22915, 2026.
The application of Fast Fourier Transform (FFT) to the amplitudes of very low frequency (VLF) signals recorded with a sampling time of 0.1 s showed that waves with wave periods below 5 s could be excited during seismic activity. The beginnings of these excitations were observed several minutes or tens of minutes before earthquake events, but studies have shown differences in the cases of earthquakes that occur during a period of intense seismic activity (PISA) and in a period without intense seismic activity (PWISA). Namely, in the first case, the Fourier amplitude is higher in the domain of wave periods from about 2 to 4 s compared to other values, while in the second case, almost discrete values of the periods in which the excitations are visible are recorded. This study presents a comparison of the characteristics of excited waves during the considered PISA and PWISA. The amplitude analysis of the 20.27 kHz ICV signal emitted in Italy and recorded in Serbia is given for one PISA in Central Italy (from 26 October to 2 November 2016) and four earthquakes that occured near Kraljevo, Serbia (Mw 5.4, and ML 4.4), in the Tyrrhenian Sea (mb 5.1), and in the Western Mediterranean Sea (ML 4.3) during PWISA (from 3 to 9 November 2010). Although more reliable conclusions require statistical analysis, the significance of the presented results lies in the indication that the aforementioned differences may indicate the possibility of a multi-day period during which earthquakes can be expected in a localized area.
How to cite: Nina, A., Eichelberger, H. U., Boudjada, M. Y., Lazović, D., and Parisi, K.: Small-period wave excitations in the amplitude of VLF signals before earthquakes: differences for periods with and without intense seismic activity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4303, https://doi.org/10.5194/egusphere-egu26-4303, 2026.
In this study we investigate the application of Artificial Intelligence (AI) Machine Learning (ML) methods – so called Transformer Architectures – to very low frequency/low frequency (VLF/LF) data sets. The research is based on electric field measurements from VLF/LF receivers of the INFREP network. The scientific objective is to characterize physical phenomena, such as variations in the electromagnetic and particle environment (e.g., solar x-ray flares), changes in ionospheric plasma parameters, and impact on the ionosphere from extraterrestrial events (e.g., gamma-ray bursts). Standard data processing algorithms in the time- and frequency domain are used to cross-check the AI/ML results. We give an overview of the status of the project, show preliminary results and discuss pros and cons of different AI/ML approaches applied to VLF/LF data.
How to cite: Srećković, V., Boyadjiev, G., Kounchev, O., Nina, A., Kolarski, A., Langovic, M., Eichelberger, H. U., and Boudjada, M. Y.: AI/ML methods applied to VLF/LF measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14301, https://doi.org/10.5194/egusphere-egu26-14301, 2026.
This contribution investigates the relationship between very low frequency (VLF) signal noise reduction and seismic activity using machine learning methods applied to VLF amplitude measurements. The problem is formulated as a binary classification task distinguishing earthquake-related intervals from non-seismic periods, using features derived from both time and frequency domains. Time-domain models show moderate performance, with the best results achieved by Support Vector Machines (AUC ≈ 0.76). In contrast, frequency-domain representations substantially enhance discriminative capability especially for the Deep Learning neural networks. Spectral features corresponding to wave periods between 0.2 and 6 s yield the strongest performance, with F1-scores up to 0.89 and AUC values reaching 0.94, while longer periods remain informative but less effective. These results provide quantitative evidence that VLF signal variations contain seismic-related signatures and demonstrate the effectiveness of spectral analysis combined with machine learning for characterizing earthquake-associated VLF anomalies.
How to cite: Bednar, P., Nina, A., Butka, P., Sarnovsky, M., Sreckovic, V., and Popovic, L.: Machine Learning Analysis of Time- and Frequency-Domain VLF Signal Variations Associated With Seismic Activity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22017, https://doi.org/10.5194/egusphere-egu26-22017, 2026.
The Romanian INFREP network, operating since 2009, monitors very low and low frequency (VLF/LF) radio signals that propagate through subionospheric reflections. The main goal is to observe and analyze variations in these signals in order to study ionospheric disturbances of natural or anthropogenic origin. Such data are important for understanding how the lower ionosphere reacts to solar and geomagnetic activity and may also provide insight into possible electromagnetic precursors of earthquakes. After more than ten years of continuous operation, some instruments in the Romanian stations began to show signs of aging and malfunction. In October 2025, a series of strong autumn storms with intense lightning affected the power supply at the Dobrogea Seismological Observatory, where an Elettronika receiver operated as part of the European INFREP network. Once power was restored, the receiver started to fail intermittently. At first, data interruptions occurred sporadically, but gradually the gaps became longer, until the receiver stopped recording completely. Errors appeared simultaneously on both the VLF and LF channels. Although the unit remained accessible and continued to produce daily log files showing frequency and time, the data were replaced by error messages. The instrument was later retrieved for inspection, but the source of the malfunction has not yet been identified. Therefore, in December 2025, the Elettronika receiver was replaced with a new one, developed jointly by the National Institute for Earth Physics (NIEP) and Integrated Project and Process Tools (IPPT). The presentation will describe the Romanian INFREP network, outline the main features of the new equipment, and compare sample recordings from both receiver generations. Early results show that the new instrument operates stably, with a high signal-to-noise ratio and uninterrupted data flow, thus improving the overall reliability of subionospheric radio wave monitoring in the region.
This paper was carried out within Nucleu Program SOL4RISC, supported by MCI, project no PN23360201, and PNRR- DTEClimate Project nr. 760008/30.12.2022, Component Project Reactive, supported by Romania - National Recovery and Resilience Plan
How to cite: Moldovan, I. A., Toader, V. E., Mihai, A., Manea, L., Anghel, M., Eichelberger, H. U., Boudjada, M. Y., Nina, A., Moldovan, A. S., Biagi, P. F., and Ionescu, C.: Monitoring of subionospheric radio wave propagation within the Romanian part of INFREP European network, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6679, https://doi.org/10.5194/egusphere-egu26-6679, 2026.
On 1 January 2024, the Mw 7.5 Noto Peninsula earthquake in Japan generated ionospheric disturbances detected via dense GNSS networks. Significant coseismic acoustic waves emerged ∼8 min post-event, exhibiting 0.3 TECU amplitudes, 2–8 min periods, and ∼1 km/s propagation speeds. These disturbances propagated exclusively southward as arc-shaped fronts. The observed anisotropy aligns closely with the local geomagnetic field orientation (declination 8.7°), suggesting magnetic channeling as a key factor. Secondary factors likely include northward thermospheric winds suppressing northward wave propagation and land-ocean coupling efficiency differences, which enhanced vertical displacements over southern continental regions. Notably, weak disturbances linked to the Mw 6.2 aftershock were detected, challenging conventional magnitude thresholds for ionospheric detection. While the mainshock's CID dynamics reflect known magnetic guidance mechanisms, the southward preference highlights site-specific interactions between seismic forcing and geophysical filters. This study provides new observational evidence of earthquake-ionosphere coupling, emphasizing the detectability of moderate-magnitude events under favorable conditions, with implications for space weather monitoring and multi-scale seismic hazard assessment.
How to cite: Zhang, B.: Successively Equatorward Propagating Ionospheric Acoustic Waves and Possible Mechanisms Following the Mw 7.5 Earthquake in Noto, Japan, on 1 January 2024, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17056, https://doi.org/10.5194/egusphere-egu26-17056, 2026.
Subsurface deposits and s-wave velocity model of the vallo di diano basin, southern italy inferred from seismic survey and borehole data
Dario Gioia(1), Giuseppe Corrado(2), Giovanni Nico (3), Marcello Schiattarella (2)
- Consiglio Nazionale delle Ricerche - ISPC, Tito Scalo (Potenza), Italy
- Università della Basilicata, DIUSS, Matera, Italy
- Consiglio Nazionale delle Ricerche - IAC, Bari, Italy
The Vallo di Diano basin (southern Italy) is a Quaternary tectonic basin of the axial zone of southern Apennines, bordered to the east by an impressive N140-150°-striking master fault. The basin-border fault of the basin represents one of the main seismogenic sources of the southern Apennine chain, and its activity has been recently correlated to stronger historical eartquakes. In this work, we introduce the results of a detailed seismic campaigns aimed at the reconstruction of the subsurface features of the basin infill. Seismic dataset includes multi-component surface-wave analysis, ESAC and HVSR along key sectors of the basin, which have been integrated to stratigraphic data coming from deep and shallow boreholes. Such data allowed us to constrain the geometry and seismic wave features of the alluvial and lacustrine deposits of the basin, providing key insights on: i) the subsoil geological model; ii) the long-term activity of basin-border faults; iii) the S-wave velocities of the continental deposits and bedrock. The infill of the tectonic basin is made of a thick succession (i.e. at least 200 m in the depocentral zone) of lower to middle Pleistocene fluvio-lacustrine deposits and coeval slope to alluvial fan deposits. Alluvial/slope and lacustrine deposits passe upward to late Quaternary palustrine sediment with a very low S-wave velocity. HVSR and ESAC data clearly depicted strong Vs contrast, which can be correlated to the lateral and vertical geometry of continental deposits. Such a complex S-wave velocity model can locally provide relevant seismic site effect, with important implications on the assessment of the seismic hazard of study area.
How to cite: Gioia, D., Corrado, G., Nico, G., and Schiattarella, M.: Subsurface deposits and s-wave velocity model of the vallo di diano basin, southern italy inferred from seismic survey and borehole data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22212, https://doi.org/10.5194/egusphere-egu26-22212, 2026.
Seismic hazards, involving the cascading effects of earthquake-induced landslides and tsunamis, can impact infrastructure networks characterized by a complexity that is increased by the climate and energy transition. Novel management policies are needed to address the associated challenges. To achieve this, approaches leveraging "Artificial Intelligence" components are frequently proposed. However, their stochastic nature demands comprehensive and quantified verification and validation (V2) results. These results can, for example, describe the probability distribution of failures and identify the most probable and worst-case failure modes for the combined system of the controlled network and management system. For geographically distributed systems, realistic V2 results must account for risks including those stemming from extreme events of seismic origin.
We present a proof of concept demonstrator to validate management and control systems operating on a power network in face of extreme events, integrating operational earthquake forecasting and seismic precursors maps.
How to cite: Quartulli, M. and Delle Femine, C.: Seismic precursors and operational earthquake forecasting impact on AI-based power network management, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22706, https://doi.org/10.5194/egusphere-egu26-22706, 2026.
Investigating the complex coupling between the lithosphere, atmosphere, and ionosphere (LAI) requires a fundamental understanding of the physical forces governing tectonic processes and their electromagnetic manifestations. While various pre-seismic signals have been successfully identified, a persistent gap remains between the empirical observation of these phenomena and the fundamental physical laws that describe nature across all scales, from the subatomic realm to cosmic expansion. Exploring these interrelations presents significant challenges due to divergent scientific languages, specialized expertise, and unique terminologies across fields. The recently approved COST Action CA24101 "Testing Fundamental Physics with Seismology" (FuSe) aims to bridge this gap by exploring how seismic phenomena and earthquake precursors can serve as a "multi-messenger" window into fundamental interactions.
At the heart of FuSe is the belief that imprints of non-standard physics, such as scalar fields or "fifth forces”, may be embedded within seismic and geomagnetic data. Conversely, theoretical insights from fundamental physics can refine our understanding of Earth’s interior by improving models of density and thermodynamic parameters like elasticity and bulk modulus. This refined modeling is essential for accurately interpreting the electromagnetic and gravitational perturbations that occur within the complex Earth-atmosphere-space system.
To ensure these breakthroughs translate into practical advancements, FuSe focuses on several strategic pillars:
- Building a common language: developing a shared methodology to equip the next generation of scientists with cross-disciplinary skills.
- Interfacing communities: creating dynamic research groups that unite scientists from particle physics, gravity, planetary science, and seismology.
- Cross-disciplinary data integration: consolidating seismic data from the Earth and Moon with particle physics and geomagnetic data into AI-ready, FAIR-compliant streams.
- SME collaboration: partnering with small and medium-sized enterprises (SME) to advance sensor networks, AI algorithms, and real-time natural catastrophe alert systems.
In this presentation, we outline the roadmap of the FuSe Action. We invite researchers with a background in electromagnetic precursors and LAI coupling to join this collaborative environment, where the synergy between geosciences and fundamental physics promises to drive innovative breakthroughs and unlock new paradigms in our comprehension of the Earth and the Universe.
This abstract is based upon work from COST Action CA24101, Testing Fundamental Physics with Seismology (FuSe), supported by COST (European Cooperation in Science and Technology).
How to cite: Piromallo, C., Strati, V., Nico, G., Wojnar, A., Apostol, E. S., Barbosa, S., Barnaföldi, G. G., Bielewicz, M., Ducobu, L., Majstorović, J., Pachol, A., Rosat, S., Sans, J. A., Tortola, M., and Zdravevski, E.: Pan-European network FuSe: a new frontier in exploring seismic phenomena and earthquake precursors, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14535, https://doi.org/10.5194/egusphere-egu26-14535, 2026.
In this study we investigate intermittent phenomena in VLF/LF electric fields and particle outbursts caused by solar activity fluctuations and affecting principally the Earth’s ionosphere. Strong events from the current solar cycle 25, e.g., x-ray flares, generate electric field amplitude and phase variations occurring on the ray-path between the VLF/LF transmitter stations and the reception facilities. These variations in the sub-ionospheric waveguide, with the lower ionosphere as upper boundary (D/E-layer during day/night), are complementary to secondary cosmic ray data measured by ground-based (muon) detectors. VLF/LF measurements are from the European INFREP receiver network and muon particle observations are collected from the Belgrade detector in Serbia. With the combined observation sets we analyze and characterize single events and corresponding statistical parameters. The study benefits from continuous ground based long-term measurements and the multi-parameter approach using complementary instrumentations.
How to cite: Veselinović, N., Eichelberger, H. U., Nina, A., Kolarski, A., Besser, B. P., Stachel, M., Wolbang, D., Solovieva, M., Biagi, P. F., Galopeau, P. H. M., Moldovan, I.-A., Nico, G., and Boudjada, M. Y.: Combined ground-based VLF/LF electric field and particle measurements related to solar variations in the solar cycle 25, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19762, https://doi.org/10.5194/egusphere-egu26-19762, 2026.
