Electromagnetic anomalous variations of the geomagnetic field, lightning activity, ionospheric F2-peak plasma frequency, GPS total electron content (TEC), etc. have been observed around the epicenter few days before the 21 September (local time) 1999 M7.7 Chi-Chi earthquake. The TEC over the epicenter anomalously and significantly decreases in the afternoon period on day 1, 3, and 4 before the Chi-Chi earthquake, which generally agrees with TEC decrease anomalies day 1-5 and day 10-15 appearing prior to M≥5.0 earthquakes in Taiwan during the 6-year period of 1994/1/1-1999/9/20. Temporal and spatial analyses of the global ionospheric map (GIM) shows that TEC anomalously and significantly decrease specifically over the epicenter day 3-4 and day 10-15 before the Chi-Chi earthquake. To find possible physical mechanisms causing the TEC decrease anomalies before the Chi-Chi earthquake, the equatorial ionization anomaly of TEC along the Taiwan longitude during September 1999 and plasma quantities of the ion density, ion temperature, and ion velocity measured by DMSP (Defense Meteorological Satellite Program) satellites are examined. It is found that westward seismo-electric fields around the epicenter area day 3-4 and day 10-15 before the Chi-Chi earthquake are essential.
How to cite: Liu, J.-Y., Wen, Y.-C., Chang, F.-Y., Lin, C.-Y., and Chen, Y.-I.: 25th anniversary study: the anomalous electromagnetic signals appear before the 21 September 1999 M7.7 Chi-Chi earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4932, https://doi.org/10.5194/egusphere-egu25-4932, 2025.
Earthquake-triggered geomagnetic variations typically exhibit time delays, with disturbances detected first at near-source stations and later at more distant locations. On April 2, 2024, a destructive M 7.4 earthquake struck the eastern Taiwan region, China, triggering an intriguing set of geomagnetic disturbances. Leveraging a high-density, three-component geomagnetic observation network with a 1 Hz sampling rate, we analyzed data from eight stations ranging from 84 to 320 km from the epicenter. Our findings reveal a striking pattern of simultaneous geomagnetic disturbances in both the X and Z components at stations within 114 km of the epicenter, with no similar disturbances observed further away. These disturbances persisted for 350 to 413 seconds, with peak amplitudes of 0.45 nT and 0.3 nT in the X and Z components, respectively. Notably, the Z-component disturbances exhibited opposite phases across the affected stations, suggesting the presence of electric currents near the epicenter. The time delay between the earthquake and the geomagnetic disturbances aligns with the expected propagation of acoustic waves from the earthquake's epicenter to the ionosphere. Using the Biot-Savart law, we estimated the location and intensity of the electric currents responsible for these disturbances. Our calculations place the currents approximately 17 km north of the epicenter, at an altitude of ~80 km, with an intensity of ~120 A and an azimuth of 301.5°. Furthermore, high-frequency Doppler sounders confirmed that acoustic waves propagated to the lower ionosphere, generating electric currents that led to the observed simultaneous geomagnetic disturbances, and continued upward to perturb the higher ionosphere. This study reveals a novel class of earthquake-triggered geomagnetic variations, offering new insights into the interaction between seismic events and the ionosphere.
How to cite: Mao, Z.: Novel Geomagnetic Disturbances Triggered by the M 7.4 Earthquake in Taiwan region: Evidence of Electric Currents, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4615, https://doi.org/10.5194/egusphere-egu25-4615, 2025.
Earthquake-induced geohydrological changes have been monitored and investigated in the last fifty years. However, most of the previous studies focused on the effects of a single earthquake event on different observations or multiple-independent events on many different data sources which arising uncertainties from different mechanisms and site effects. The quantitative analysis of earthquake-induced geohydrological changes and their effects on soil liquefaction remains a challenge. In order to complete the soil liquefaction potential map in Taiwan and improve the accuracy of the analysis and evaluation, the Central Geological Survey of the Ministry of Economic Affairs conducts a six-year plan from 2018 to 2023. The geological and geohydrological data thoroughly collected by previous projects serve as a solid foundation for this 4-year project to systematically probe the coseismic geohydrological changes and their effects on soil liquefaction.
In the four year of this project, four primary tasks had been finished including (1) database establishment of the long-term groundwater level observations in the study areas, (2) three-dimensional hydrogeological structures construction of the study areas,, (3) case study of induced groundwater level changes and liquification in three catastrophic earthquakes (4) methodology development and establishment of the coseismic geohydrological changes and their effects on soil liquefaction potential.
The establishment and management of the long-term groundwater level observations in the study areas were done in this year. The statistical program was merged into processing procedures for data analysis. Also, external observational data produced by the Water Resources Agency and Central Weather Bureau was integrated. The three-dimensional hydrogeological models were established based on the models constructed in T-PROGS (Transition Probability Geostatistical Software). With limited drilling data, the three-dimensional hydrogeological models could be applied to estimate and build an underground database for those areas with no data. In addition, the geological zoning after geological research and judgment could serve as a reasonable geological basis for subsequent interpolation of soil liquefaction.
The hourly and secondly data of groundwater level variations and the hourly river discharge variations triggered by the 1999 Chi-Chi earthquake, 2016 Meinong earthquake and 2018 Hulien earthquake are checked and analyzed to investigate the responses under different hydrogeological conditions in west and south regions of epicenter. The increased groundwater levels are shown to consistent with the horizontal peak ground velocity (PGV), which imply that the increased groundwater levels might result from the buildup pore water pressure induced by shear strain, like the liquefaction mechanism.
Uncertainties associated with groundwater level measurement or incorrect representation of regional groundwater level could easily lead to erroneous assessments of liquefaction potential in regional areas. These uncertainties result from spatial and temporal groundwater level variability and/or measurement error. Natural variability also makes it difficult to correctly identify the groundwater depth. The groundwater level fluctuates in response to recharge and discharge. In this project, an alternative methodology was adopted in order to overcome these inherent uncertainties.
How to cite: Lai, W.-C., Wang, S.-J., and Lin, Y.-Y.: The study of coseismic geohydrological changes and its effects on soil liquefaction potential in Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3450, https://doi.org/10.5194/egusphere-egu25-3450, 2025.
In this research, we explore the EM response generated by earthquake fault-slip attributable to the piezomagnetic effect. To achieve this, we integrate the elastodynamic equations with Maxwell's equations. We put forward a semi-analytical method for simulating seismo-electromagnetic fields within a horizontally-stratified model. In this model, the coupled equations are resolved in the frequency-wavenumber domain. Subsequently, the seismo-electromagnetic responses in the time-space domain are obtained through the Hankel transform and the inverse Fourier transform. We carry out numerical simulations to examine the characteristics of the EM signals triggered by a fault - slip source. The results indicate that the piezomagnetic effect can generate both magnetic and electric fields. For an Mw 6.0 earthquake, at a receiver 85 km from the epicenter, the coseismic electric field can reach approximately ~0.1 μV/m, and the coseismic magnetic field can reach about 0.1 nT. This demonstrates that the EM fields resulting from the piezomagnetic effect are detectable by current EM equipment. Furthermore, we apply this method to simulate the observed coseismic EM data from an actual earthquake. The predicted magnetic fields show a high degree of consistency with the data, validating the effectiveness of our method.
How to cite: Gao, Y. and Zhao, J.: Modeling of electromagnetic fields generated by an earthquake due to piezomagnetic effect, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6273, https://doi.org/10.5194/egusphere-egu25-6273, 2025.
Over the past 10 years, increasingly intensive studies of ionospheric plasma structures have been carried out using data from the Low-Frequency Array for radio astronomy (LOFAR) radio telescope system. Recently more and more attempts are taken to combine LOFAR ionospheric studies with other monitoring techniques such as GNSS observations. LOFAR detects scattering of high-frequency (HF) (MHz) electromagnetic waves (EMW) on the above-mentioned plasma structures. Astrophysical sources of such EMWs may be, for example, radio galaxies, supernovae remnants and pulsars. The plasma structures under investigations are excited due to impacts on the ionosphere “from below”, namely powerful natural hazards, including typhoons, volcanoes and earthquakes, and “from above”, in particular strong magnetic storms, accompanied by corresponding disturbances of auroral currents and due to flows of charged particles; as well as because of solar flares, eclipses and the terminator, as well as various plasma instabilities and nonlinearities, etc. Now we are focusing on identifying quasi-periodic and quasi-wave ionospheric disturbances in the low frequency range, including traveling ionospheric disturbances (TIDs). Results will be presented (1) based on developed models of linear and nonlinear TIDs in the presence of corresponding linear and nonlinear atmospheric gravity waves (AGWs); (2) appropriate modulation of the ionospheric plasma; (3) examples of scattering of high-frequency (HF) (MHz) electromagnetic waves (EMWs) on plasma structures, including the characteristics of the Doppler shift on moving plasma structures, taking into account birefringence in ionospheric plasma, as well as results regarding the qualitative influence on the scattering characteristics of EMWs such factors as height and horizontal dimensions of the ionospheric plasma scatterer. Algorithms are being developed to take into account the influence of plasma resonances and photochemical interactions on the characteristics of emerging ultra-low frequency (ULF) plasma structures. A database has been created that includes dynamic spectra of plasma disturbances with reference to the times of sunrise and sunset over a number of months in 2024. Observations of plasma structures were carried out at various LOFAR stations. Slant TEC maps are being developed on the basis of GNSS data. Spectral processing (using in particular Fast Fourier Transform, wavelets and transformation from dynamic spectra to Doppler shifter spectra) of the LOFAR and GNSS data is carried out with the aim of identifying quasi-periodic and quasi-wave ultra-low frequency (ULF) plasma structures with subsequent comparison “Theory-Experiment”.
How to cite: Rapoport, Y., Krankowski, A., Błaszkiewicz, L., Grimalsky, V., Fron, A., Kotulak, K., Flisek, P., Petrishchevskii, S., and Grytsai, A.: Modeling and experimental investigations for Modern Radio-Diagnostics of the impacts on ionosphere “from above and from below” using LOFAR and GNSS Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5623, https://doi.org/10.5194/egusphere-egu25-5623, 2025.
Electromagnetic response to undersea earthquakes in a layered ocean model Qianli Cheng, Yongxin Gao We adopt a horizontally layered model consisting of air, seawater and undersea porous rock and develop an analytically based method to calculate the seismic and electromagnetic (EM) fields generated by undersea earthquakes. We conduct numerical simulations to investigate the characteristics of the EM response at the receivers located at the seafloor, in the seawater near the sea surface and in the air, respectively. The results show that two kinds of EM signals can be identified in the EM records at these receivers, namely, the early EM wave (seismic-to-EM conversion at the seafloor interface) arriving before the seismic waves and the coseismic EM fields with apparent speeds of the seismic waves. The EM signals observed at the seafloor are mostly stronger than those observed in the seawater and air near the sea surface. The method is applied to simulating the EM response to the 2022 Mw 7.3 earthquake that took place in the sea near Fukushima, Japan. At a receiver with 76 km epicentral distance at the seafloor, the predicted coseismic electric and magnetic signals reach 2 μV/m and 2 nT, respectively, which are within the detectability of the current EM equipment. This suggests a possibility to monitor the EM disturbances associated with undersea earthquakes and use them to serve the earthquake early warning, helping to mitigate the societal impact of large earthquakes.
How to cite: Cheng, Q. and Gao, Y.: Electromagnetic response to undersea earthquakes in a layered ocean model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20874, https://doi.org/10.5194/egusphere-egu25-20874, 2025.
How to cite: Zhang, J., Hu, H., and Gao, Y.: Global Analytical Simulation of Acoustic-Gravity Wave Propagation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7929, https://doi.org/10.5194/egusphere-egu25-7929, 2025.
In the measurement of water current velocities, sound waves are commonly used to detect the Doppler effect caused by small scattering particles. The widely known Acoustic Doppler Current Profilers (ADCPs) operate based on this principle (Gould et al., 2001). Although ADCPs are widely used for measuring water current velocity, single-point current meters are considered a better choice for precise and continuous measurements of near-seafloor water current velocity.
In this study, a single-point current meter (Aquadopp-6000m Current Meter) was mounted on the Yardbird-BB OBS (Lin et al., 2024) to form a Seafloor Current Meter (SCM). The SCM was used to measure and record water current disturbances above the OBS seismic sensor. The data collected by the SCM can be used not only for analyzing the overall OBS orientation, the time of contact with the seafloor, the moment the seismic sensor detached from the A-frame and settled onto the seafloor, and the sound speed, temperature, and pressure profiles during the instrument's descent, but also for broader applications.
By increasing the sampling rate to 1 sps, the continuous observation data can be analyzed alongside OBS data to study the relationship between background seismic noise and seafloor current velocity, as well as changes in seafloor current velocity before and after seismic events. Moreover, atmospheric pressure changes—occurring even thousands of kilometers away before a typhoon forms—can affect seawater pressure, seafloor current velocity, and subtle variations in seafloor temperature, which in turn influence ocean sound speed.
This study analyzes and discusses SCM data collected in the northeastern offshore waters of Taiwan, at the western end of the Okinawa Trough..
Reference:
Gould, J., B. Sloyan, and M. Visbeck. (2013). In Situ ocean observations: a brief history, present status and future directions. In, G. Siedler, S. Griffies, J. Gould, and J. Church. (eds.) Ocean Circulation and Climate: A 21st Century Perspective. 2nd Ed. (HASH(0xa0a5e98), Oxford, GB. Academic Press, pp. 59-82. https://eprints.soton.ac.uk/358924/
Lin, C.R., Y.C. Liao, C.C. Wang, B.Y. Kuo, H.H. Chen, J.P. Jang, P.C. Chen, H.K. Chang, F.S. Lin and K.H. Chang. (2024). Development and evaluations of the broadband ocean bottom seismometer (Yardbird-BB OBS) in Taiwan. Terr Atmos Ocean Sci. 35, 4. Doi: https://doi.org/10.1007/s44195-024-00062-w
How to cite: Lin, C.-R.: Data Collection and Applications of Seafloor Water current Velocity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2355, https://doi.org/10.5194/egusphere-egu25-2355, 2025.
Seismic velocity is particularly sensitive to clay degradation, measuring relative seismic velocity (dv/v) with seismometers has emerged as a powerful geophysical technique for monitoring ground surface activities. Previous studies have considered the seismic velocity variations over large-scale area under seasonal weather while neglecting the impact of short-term rainfall on clay landslides. We aim to elucidate the quantitative variations of dv/v on shallow clayed slope measured by short-distance sites under rainfall influence. In this study, we deployed five seismometers and one rain gauge on the Juemo Village landslide (Sichuan Province, China) from June 21, 2022, to September 12, 2022. The cross-correlation method was employed to calculate the variations in the travel time of the same seismic phase between two seismic sites. The results show a clear drop in velocity under rainfall conditions, with a relative variation of approximately 15%. The observations could enhance the recognize of slope failure related to rainfall and provide a possible indicator of landslide early warning.
How to cite: Liu, Y. and wang, F.: The Variation Characteristics of Delay Times of Seismic Signals in Shallow Slopes Under Rainfall Conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5426, https://doi.org/10.5194/egusphere-egu25-5426, 2025.
Earthquakes are potentially one of the most catastrophic natural hazards. Predicting earthquakes has always been a dream; presently, this is still impossible. However, there are several pieces of evidence for good candidates of pre-earthquake signals recorded as variations in lithosphere, atmosphere and ionosphere. From a theoretical point of view, several theories of propagation of anomalies generated in the lithosphere upward in the atmosphere and even in the ionosphere have been proposed: a pure electromagnetic Ultra-Low_Frequency wave (e.g., Molchanov and Hayakawa, 1995, https://doi.org/10.1029/95GL00781), an electrochemical model for producing positive charges from the increase of stress on the faults (Freund, 2011, https://doi.org/10.1016/j.jseaes.2010.03.009), a chemical and physical chain of processes based on air ionization induced by radon (Pulinets and Ouzounov, 2011 https://doi.org/10.1016/j.jseaes.2010.03.005) or a mechanical wave propagating vertical to the ionosphere induced by temperature increase of Earth’s surface, known as Acoustic (or atmospheric) Gravity Wave (https://doi.org/10.1541/jae.31.129). In this presentation, several pieces of evidence of candidates for pre-earthquake signals for the different mechanisms of coupling will be shown. The examples are collected from the analyses of medium-large earthquakes, such as Mw = 6.7 Lushan (China) 2013 (Zhang et al., 2023, https://doi.org/10.3390/rs15061521), Mw = 7.5 Indonesia 2018 (Marchetti et al., 2020, https://doi.org/10.1016/j.jseaes.2019.104097), Mw = 7.7 Jamaica 2020 (Marchetti et al., 2024, https://doi.org/10.1016/j.rse.2024.114146), Mw = 7.2 Haiti 2021 (Marchetti, 2024, https://doi.org/10.3390/geosciences14040096) and other seismic events.
It’s proposed that different models of Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) describe different ways and mechanisms of interactions between the geo-layers of the Earth system. In this frame, one theory does not necessarily exclude another one. Still, the reasons for a specific coupling mechanism require to be further investigated. Among them, focal mechanisms, sea or land location, and geological constraints could play a main role in a coupling or another one.
How to cite: Marchetti, D.: Clues of multiple Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) mechanisms before the medium-large earthquake occurrence, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13854, https://doi.org/10.5194/egusphere-egu25-13854, 2025.
Disturbances occurring near the Earth's surface, such as earthquakes, tsunamis, volcanic eruptions, typhoons, and hurricanes, can trigger severe perturbations or fluctuations in the ionosphere. These perturbations or fluctuations typically have periods of tens of minutes and propagate outward from their origin at speeds of several hundred to thousands of meters per second. Most previous studies have utilized Total Electron Content (TEC) observations from dense ground-based Global Navigation Satellite System (GNSS) receiver networks to monitor the horizontal propagation of these perturbations or fluctuations. On the other hand, these disturbances or fluctuations also propagate vertically upward, penetrating the atmosphere and disturbing the ionosphere. Several studies have employed multiple ground-based instruments, such as seismometers, infrasound systems, magnetometers, high-frequency Doppler sounding systems, ground-based GNSS receivers, and ionosondes, to detect and investigate the vertical propagation of these perturbations. These studies have demonstrated the importance and complexity of disturbances originating from the lithosphere. Due to the scarcity of instruments primarily installed on land, observing and studying vertical disturbances remain challenging. Therefore, radio occultation (RO) techniques on Low Earth Orbit (LEO) satellites, which globally detect atmospheric and ionospheric structures, provide valuable insights for monitoring and studying phenomena in regions lacking ground-based instruments, such as oceans, deserts, and polar areas. This presentation introduces the use of RO techniques from the FORMOSAT-3/COSMIC (F3/C) and FORMOSAT-7/COSMIC-2 (F7/C2) missions to monitor ionospheric vertical disturbances caused by events such as the magnitude 9.0 Tohoku earthquake on 11 March 2011, the magnitude 7.8 Nepal earthquake on 25 April 2015, and the underwater volcanic eruption near Tonga on 15 January 2020, etc. The results show that intense disturbances originating from the lithosphere should be regarded as significant drivers that alter ionospheric structures and dynamics. Studying vertical disturbances benefits us understand the propagation of fluctuations and dynamic changes across various geospheres.
How to cite: Sun, Y.-Y.: Ionospheric Vertical Disturbances Induced by Lithospheric Activities: Insights from Radio Occultation Technique, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6483, https://doi.org/10.5194/egusphere-egu25-6483, 2025.
On September 16, 2021, an Ms 6.0 earthquake occurred in Luxian, Luzhou City, Sichuan Province, China, following the Ms 6.0 Changning earthquake on June 17, 2019, another significant seismic event in the Sichuan Basin. The epicenter of the Luxian earthquake was situated within the NE-trending Huaying Mountain Folded Fault Zone, and the maximum seismic intensity reached Level VII, resulting in 3 fatalities and 159 injuries. Some studies propose that this earthquake may be associated with the development of nearby shale gas extraction platforms, exhibiting characteristics of both induced and natural seismicity, thereby holding considerable research significance. This study identifies multiple pre-seismic anomalous signals preceding the Luxian Ms 6.0 earthquake, including total electron content (TEC), geomagnetic variations, velocity structure changes, b-value fluctuations, and fault stress anomalies. Employing machine learning techniques, Log-Periodic Power Law (LPPL) models, and other analytical methods, we conduct a comprehensive assessment of the indicative capacity and predictive efficacy of these pre-seismic anomalies. The findings reveal that certain anomalous signals exhibit predictive relevance concerning the key parameters of the mainshock. Furthermore, the seismic mechanisms of medium- to strong-magnitude induced earthquakes appear to be similar to those of natural earthquakes, potentially demonstrating more pronounced and sustained pre-seismic anomalies. The coupled analysis of these signals offers valuable insights for improving the prediction of future high-magnitude seismic events.
How to cite: Wang, X. and Hu, J.: Coupling Diverse Pre-Seismic Anomaly Features for Inferring Critical Information on the Ms6.0 Earthquake in Luxian, Sichuan, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14339, https://doi.org/10.5194/egusphere-egu25-14339, 2025.
The ionosphere is part of the space above 60 to 1000 km from the ground and is an important part of near-earth space. The study of the ionosphere is conducive to providing better understanding the coupling interaction features within the lithosphere, atmosphere and ionosphere, exploring the possible associations between earthquake precursors and ionosphere disturbances, providing services for human activities and more approaches for disaster prevention and mitigation.
A chaotic coding ionosonde was developed in Yinchuan, Ningxia Hui Autonomous Region, China, in 2021. The ionosonde scans in 1~30 MHz frequency range, with the distance resolution of 1.5km and detection height from 67.5 km to 560 km. It utilizes technologies of pulse compression and chaotic coding, suppresses clutter interferences successfully and obtains high quality ionograms. This ionosonde operates automatically and produces an ionogram every 15 minutes. A multiscale transformer neural network is utilized for the extraction of echo traces and accurate inversion of the ionospheric parameters, such as the critical frequence of F2 layer, the minimum reflection height, the separation of traces of the F layer's O/X waves as well as the electron density profile based on an improved bottom inversion model of the International Reference Ionosphere.
Several strong ionospheric disturbances were observed in 2023 and 2024. In April and November 2023, massive solar flare eruptions caused geomagnetic disturbances, and the F2 layer responded to the disturbances obviously in term of the critical frequence and the traces of the F layer's O/X waves. In December 2023 two earthquakes with ML ≥ 4 happened in Gansu province, and also there were solar flare eruptions during that period. Some ionospheric disturbances were observed by the ionosonde approximately two or three weeks before the earthquakes. Besides, the fluxgate sensors and magnetometers installed on the geomagnetic stations in Gansu province and Ningxia Hui Autonomous Region also recorded the disturbances in the daily curves, synchronous with the ionosonde records. In January and February 2024, some typical U-shaped and sickled-shaped traces are observed in the ionograms, which are considered to be the phenomena caused by traveling ionospheric disturbances (TIDs). Some other disturbance phenomena are also recorded by the ionosonde, including the traces diffusion, partial disappearance, abnormal shapes, etc., worthy of research in multiple fields combining the lithosphere, atmosphere, ionosphere and space physics.
How to cite: Wang, C. and Cui, H.: Observation and Research of Strong Ionospheric Disturbances Using a Chaotic Coding Digital Ionosonde, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2989, https://doi.org/10.5194/egusphere-egu25-2989, 2025.
Based on the two Sheveluch eruption events on April 10, 2023 and August 17, 2024, the comprehensive phenomenon of the two volcanic eruption events is described from the analysis of the seismic activity sequence of the lithosphere to the distribution of atmospheric materials and heat. The seismic distribution in Sheveluch volcanic area is mainly shallow-source (0-70 km) and small-earthquake (ML 3.5-4.0). In term of the horizontal evolution of SO2, the SO2 eruption amount and the duration on April 10, 2023 is larger and longer than on August 17, 2024. In the time series, SO2 and UV aerosol index obviously respond to the volcano eruption activity. In the vertical dimention, the vertical wind field data show that the SO2 eruption height is about 100~125hpa, and the boundary layer height between the troposphere and the stratosphere in the Sheveluch volcano region is about 50hpa. The noticeable variation of the temperature profile of the two volcanic eruptions was below 10hpa. Comparing the ozone profile with the temperature profile, the ozone depletion may result in a decrease in stratospheric temperature. The horizontal and vertical migration processes of atmospheric materials during volcanic eruption are described, which is of great significance for the study of multi-layer coupling mechanism.
How to cite: Liu, Q., Gui, L., Ma, X., Xu, J., and Shen, X.: Atmospheric physicochemical multi-parameter horizonal and vertical mitigation response of two recent Sheveluch volcano eruptions in Kamchatka, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7648, https://doi.org/10.5194/egusphere-egu25-7648, 2025.
A FORMOSAT-5 (FS-5) satellite was launched on 25 August 2017 CST into a 98.28° inclination sun-synchronous circular orbit at 720 km altitude along the 1030/2230 local time sectors. Advanced Ionospheric Probe (AIP), a piggyback science payload developed by National Central University for the FORMOSAT-5 satellite, has measured in-situ ionospheric plasma concentrations at a 1,024 Hz sampling rate over a wide range of spatial scales for more than 7 years. Dramatical ionospheric plasma density and velocity modulation caused by natural hazards like 2022 Hunga Tonga–Hunga Haʻapai eruption and 2024 Mother Day geomagnetic storm had been observed clearly by FS-5/AIP and will be presented in the talk.
How to cite: Chao, C.-K. and Huang, W.-R.: Ionospheric Plasma Response to Natural Hazards Observed by Advanced Ionospheric Probe Onboard FORMOSAT-5 Satellite, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3188, https://doi.org/10.5194/egusphere-egu25-3188, 2025.
An M7.4 magnitude earthquake struck Hualien, Taiwan, on April 3, 2024, at 07:58:12 local time. We collected data from ground-based Global Navigation Satellite System (GNSS) receivers near the epicenter and retrieved coseismic displacements using precise point positioning (PPP) and ionospheric total electron content (TEC) from dual-frequency phase observations received from geostationary Earth orbit (GEO) satellites. The TEC data reveal not only coseismic ionospheric disturbances occurring ~10 minutes after the earthquake, but also disturbances occurring ~1 minute post-event, which are time-synchronized with the coseismic displacements. This type of TEC disturbance is consistently observed across three stations. We projected the displacement in two directions: the line-of-sight (LOS) between the satellite and receiver, and the normal plane to the LOS. The trends in TEC are consistent with the displacements projected onto the LOS normal plane, with a magnitude relationship of approximately 0.05 TECU increase in TEC per 10 cm increase in displacement. In contrast, displacements projected along the LOS direction do not show the same trends in TEC. Therefore, we confirm that LOS movement caused by seismic shaking of GNSS receivers affects the calculation of GNSS-based GEO-TEC.
How to cite: Rao, H.: Seismic shaking recorded simultaneously on TEC and PPP: a case study of the Hualian earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4721, https://doi.org/10.5194/egusphere-egu25-4721, 2025.
In this study, we analyzed ionosonde observations in Eastern Asia to investigate the responses of the sporadic E (Es) layer to severe atmospheric disturbances caused by the Tonga volcanic eruptions on 15 January 2022. The most notable feature observed was the disappearance of the Es layer after approximately 10:00 UT, attributed to the vertical drift induced by the eruptions. The Es layer reappeared intermittently after 13:00 UT, coinciding with the arrival of the tropospheric Lamb wave. To understand the mechanism behind this intermittence, we also analyzed horizontal wind data in the mesosphere and lower thermosphere regions, recorded by meteor radars. Wind disturbances with periods of approximately 20 hours contributed to the nighttime formation of the Es layer on January 15.
How to cite: Wang, J. and Sun, Y.-Y.: Sporadic E responds to the 2022 Tonga volcano eruptions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20923, https://doi.org/10.5194/egusphere-egu25-20923, 2025.
Elastic wave velocity comprehensively reflects the internal physical changes of a slope and offers significant advantages in monitoring. However, existing research rarely considers the impact of soil structure changes on wave velocity. This paper focuses on the Juemo Village landslide, examining the effects of soil structure, hydrological parameters, and stress on wave velocity during the deformation and evolution of rainfall-induced landslides. The study employs both soil unit and slope model scales to reveal the internal response mechanisms. The results indicate that during the relatively stable stage of the landslide, the increase in water content and pore water pressure alters the proportion of the three-phase medium, resulting in a gradual decline in wave velocity. In the slow deformation stage, the soil particle skeleton remains largely intact, with minimal changes to the elastic wave propagation path, leading to a stable wave velocity. As the slope undergoes accelerated deformation approaching the critical sliding stage, stress causes a rapid increase in soil particle porosity and a significant reduction in particle contact area. Consequently, the elastic wave propagation path increases sharply, leading to a rapid decline in wave velocity. A deeper understanding of the response mechanisms of elastic wave velocity provides a theoretical foundation for constructing wave velocity-based early warning models and enhances the internal monitoring and early warning systems for rainfall-induced landslides.
How to cite: Wang, F., Zhong, K., Zhao, J., Chen, J., and Ma, L.: Experimental study on elastic wave velocity response mechanism of rainfall-induced landslide deformation evolution process, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20889, https://doi.org/10.5194/egusphere-egu25-20889, 2025.
Using the Load/Unload Response Ratio (LURR) method to identify sub-instability before large earthquakes seems to be a critical advancement in earthquake prediction and understanding the processes leading up to seismic events. By analyzing various earthquake-related observation data and discriminating between load and unload phases at observation stations, researchers were able to detect anomalies in stress states that indicate the potential for large earthquakes. The findings from retrospective studies on past earthquakes, such as the ones in Jiashi, Xinjiang, Menyuan, Qinghai, and Luding, Sichuan, provide significant evidence that LURR anomalies exceeding 2 standard deviations of the mean were observed at observation stations near the epicenter before the mainshocks. The decreasing distance between stations detecting LURR anomalies and the epicenter as the mainshock approached suggests a correlation between these anomalies and the impending earthquake. Overall, the identification of sub-instability through the LURR method and the spatio-temporal evolution of these anomalies could provide valuable insights into the weakening processes in the source media leading up to large earthquakes. This research has the potential to contribute to improved earthquake forecasting, ultimately enhancing our ability to mitigate the impacts of seismic events.
How to cite: Yu, H., Li, G., Yang, W., and Yuan, Z.: Exploration of sub-instability before large earthquakes with the LURR method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1238, https://doi.org/10.5194/egusphere-egu25-1238, 2025.
A MS6.8 earthquake struck Luding Country in Ganzi Prefecture, Sichuan Province on September 5, 2022. The earthquake occurred on the Moxi segment of Xianshuihe fault zone (XFZ), one of the most seismically active faults in the China mainland. In this study, multiple periods of the Global Positioning System (GPS) velocity fields and continuous observational data are collected to analysis the tectonic deformation and evolution characteristics before the Luding earthquake, from the perspectives of the kinematic behaviors of seismogenic faults, the multi-scale strain features around the study region, and the variation of GPS baseline across the epicenter area. Then the following conclusions are obtained: (1) The accelerated compression of baselines SCGZ-SCXJ and SCLH-SCXJ in Bayan Har block indicate that boundary faults are decoupling and accelerated southward and eastward pushing under the influence of the coseismic rupture of Maduo MS7.4 earthquake, which leads to the acceleration of the strain accumulation and the increase of seismic risk in the divergence area bounded by the southern section of XFZ and the southwestern section of Longmenshan fault zone (LFZ). (2) Luding earthquake located in the weakened region around the edge of the large strike-slip fault zone with high shear strain rate, and the tensile zone of the strain perpendicular to the fault direction, denoting that the reduction of the normal strain in the locked background is strongly related to fault rupture and earthquake nucleation.
How to cite: Yuan, Z. and Yu, H.: Study on Deformation Characteristics of Southeastern Tibetan Plateau and Dynamic Cause of the Luding MS6.8 Earthquake, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6503, https://doi.org/10.5194/egusphere-egu25-6503, 2025.
The onset of landslides is often preceded by rock fracturing and strata failure, processes that can emit electromagnetic radiation. To analyze the relationship between magnetic perturbations and landslides, we systematically excluded influences from solar activity, lightning, artificial noise, and seismogenic faults. Using the correlation coefficient method, we examined the in-phase and out-of-phase relationships within geomagnetic data collected from approximately 100 monitoring stations. The analysis revealed that correlation coefficients exceeding 0.8 (high) and below -0.8 (low) related to landslides are distributed across areas with an extensive radius of approximately 500 km. Two distinct interfaces were identified between high (>0.8) and low (<-0.8) correlation coefficients, extending from the landslide sites. These interfaces aligned with the direction of the landslide flow and its perpendicular direction. We hypothesize the presence of two electric currents flowing along these interfaces and applied the Biot-Savart Law to compute the associated magnetic perturbations. The computed results show a reasonable agreement with observational data. Furthermore, the detection of electromagnetic radiation several minutes before landslide events suggests the potential for an early warning system. By leveraging far-field geomagnetic data, such a system could help mitigate fatalities and reduce risks associated with landslides.
How to cite: Chen, C.-H., Yisimayili, A., Chen, L., Wang, F., and Luo, T.: Landslide-Triggered Large-Scale Electromagnetic Perturbations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2844, https://doi.org/10.5194/egusphere-egu25-2844, 2025.
We report on the lower ionospheric anomalies observed around the occurrence time of the Noto Peninsula Earthquake (M7.5) on January 1, 2024. A case study was conducted based on the continuous time series data of the electric field amplitude acquired by the VLF/LF-transmitter signal-receiving network operated by the University of Electro-Communications in Japan. We used the nighttime fluctuation method to analyze the data and derived the daily changes in (1) trend (the average of the nighttime average amplitude fluctuations) and (2) dispersion (the variance of the nighttime average amplitude fluctuations). As a result, a decrease in trend was observed in 4 of the 8 transmission-reception paths 6 to 9 days before the earthquake. An increase in dispersion was also observed in conjunction with the decrease in trend. These characteristics indicate a short-term lower ionosphere anomaly before earthquakes. For the 2 paths close to the epicenter, a remarkable increase in dispersion was observed one day before the earthquake. This anomaly shows the imminent precursor of the earthquake that contains clear oscillations in electric amplitude in the period of 30 – 240 minutes, implying the LAI coupling due to AGW. The simultaneous occurrence of propagation paths also indicates the spatial extent of the earthquake preparation zone.
How to cite: Hobara, Y., Shvets, A., and Hayakawa, M.: Preliminary analysis of lower ionospheric perturbations using VLF/LF transmitter signal associated with 2024 M7.5 Noto Peninsula earthquake in Japan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20397, https://doi.org/10.5194/egusphere-egu25-20397, 2025.
Most of the ten destructive earthquakes that occurred in Taiwan in the 20th century were located in the deformation front area of the southwestern Taiwan. Therefore, it is necessary to conduct a detailed study on the seismic characteristics of this area. In order to effectively prevent earthquake-induced disaster risks in urban areas, this study aims to enhance high-resolution imaging of seismogenic structures and capture microseismic signals using a dense array at the front of the orogenic belt. Understanding the structure of the fault provides important data for modeling earthquake events and can help improve earthquake risk assessments in the region. Since deep learning neural network methods are widely used in earthquake-related research, phase picking is the most critical first step in seismic data processing. This study used a large number of microseismic events observed by a dense array deployed from 2020 to 2023 to explore possible potential seismic structures beneath the front edge of the foothill belt in order to understand the rupture mechanism and tectonic evolution process of the unknown seismic structure. This study used the initial earthquake catalog generated by AI automatic phase picking technology and used hypoDD to relocate microseismic events. By the way, the DBSCAN algorithm is used to find clusters where a large number of microearthquakes occur. The final relocation results showed that there was a west-dipping seismic belt and multiple east-dipping seismic belts at depths of 5 to 15 km, and an earthquake swarm was found at a depth of 15 km. According to the grouping algorithm and stress inversion results, the maximum stress axis in this area is mainly northwest-southeast, reflecting the direction of compressive stress since the orogenic process.
How to cite: Wen, S., Tsai, W.-T., and Kuo, Y.-S.: High seismic potential areas along the collision front in southwestern Taiwan revealed from dense array analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3764, https://doi.org/10.5194/egusphere-egu25-3764, 2025.
Contemporary navigation, communications, and electronic warfare systems heavily depend on the uninterrupted accessibility of Global Positioning Satellite Systems (GNSS) or comparable systems for the purposes of location determination, navigation, and time synchronization (PNT). Irrespective of the deliberate or inadvertent nature of the purpose, the act of Global Navigation Satellite System (GNSS) jamming, also known as ja mming, has the potential to significantly impede or entirely interrupt applications that depend on Positioning, Navigation, and Timing (PNT). Therefore, the assurance of PNT functionality emerges as an essential imp erative. Due to the inherently weak power of normal GNSS signals, the operational integrity of these systems and the effective completion of their tasks might be compromised by the interference caused by low-cost G NSS jammers. In the present study, the phenomenon of localized scintillation structure, characterized by the disruption of radio signals due to abnormalities, is duly acknowledged. The presence of irregularities within the ionosphere can have an impact on the propagation of radio waves passing through it. In this study, a low-cost GNSS network is established in the Ta i w a n region utilizing Septentrio GNSS mosaic X5 modules. The purpose of this network is to monitor the quality of the GNSS signal and determine whether any interference originates from ionospheric abnormalities or the local RF environment.
How to cite: Hsiao, T.-Y.: The Monitoring of Localize Ionospheric Scintillation and RF Interference by GNSS Network, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20023, https://doi.org/10.5194/egusphere-egu25-20023, 2025.
Recent advances in machine learning, particularly neural networks, have paved the way for innovative approaches to predicting geophysical phenomena. This study explores the integration of solar activity data with neural network methodologies to classify and predict seismic events and geomagnetic disturbances. Two case studies were utilized: the classification of seismic events influenced by solar activity using a Long Short-Term Memory (LSTM) model, and geomagnetic disturbance predictions via K-index classification employing neural networks.
The first case study utilized proton density data from the Solar and Heliospheric Observatory (SOHO) and seismic records from the U.S. Geological Survey (USGS). The LSTM model achieved an accuracy of 84.47% in classifying seismic events, highlighting the significance of proton density variations as precursors to seismic activities. Weighted learning techniques addressed data imbalance, enabling accurate classification of rare seismic occurrences.
In the second case study, geomagnetic data from the Almaty Geomagnetic Observatory was analyzed. A neural network model optimized for K-index classification achieved a remarkable 98% accuracy, demonstrating the robustness of neural architectures in space weather prediction. Temporal dependencies and diurnal cycles in geomagnetic disturbances were captured effectively, underscoring the utility of advanced machine learning techniques in understanding Earth's magnetic environment.
The combined findings affirm the potential of integrating solar activity data with neural network frameworks for geophysical forecasting. This approach not only enhances disaster preparedness but also contributes to the theoretical understanding of the interplay between solar and terrestrial dynamics. Future research should focus on extending these methodologies to broader datasets and incorporating additional physical parameters for improved predictive reliability.
How to cite: Zhumabayev, B., Nurtas, M., and Sarsembayeva, A.: Integrating Solar Activity and Geomagnetic Disturbance Techniques with Neural Networks for Geophysical Event Prediction: Insights from Seismic Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11164, https://doi.org/10.5194/egusphere-egu25-11164, 2025.
Before a strong earthquake occurs, the phenomenon of accelerated release of strain energy is common in the area near the epicenter, indicating that the seismogenic area is approaching or entering a critical state. Taking the Benioff strain as the response quantity, the Benioff strain ratio at different periods is calculated, which can be used as a parameter to characterize the speed of strain energy release, and its abnormal evolution reflects the high-stress state of the intermediate substance during seismic nucleation. Using the catalog provided by China Earthquake Networks Center, the Benioff strain ratio of 90 days per month was calculated one year before the M6 earthquakes in Xinjiang since 2000 on the basis of analyzing the completeness thresholds magnitude. The results show that 14 of the 18 groups’ earthquakes were located in the high-value anomalies region within one year,passing the prediction effect test, which indicates that the high-value anomaly of the Benioff strain ratio has mid-short term prediction significance for M6 earthquakes in Xinjiang region. Taking the Aketao M6.7 earthquake and Hutubi M6.2 earthquake in 2016 as examples, the strain ratio in the seismogenic zone showed the characteristics of "gradually increasing - rapidly decreasing - stable fluctuation" within one year before the earthquake, which may be related to the instability nucleation process of the fault.
How to cite: Yang, W., Yu, H., Li, G., and Yuan, Z.: Research on the features of the Benioff strain ratio in Xinjiang region before earthquakes above MS6.0, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1158, https://doi.org/10.5194/egusphere-egu25-1158, 2025.
On January 8, 2022, an MS6.9 earthquake occurred in Menyuan County, Qinghai Province, China. The epicenter was located in the tectonic transition zone between the Lenglongling fault and the Tuolaishan fault on the northeastern Qinghai-Tibet Plateau. Starting from July 2021, based on the increased seismic activity of magnitude 5 or above in the central and northern regions of the Qinghai-Tibet Plateau, as well as a significant increase in the number of short-term geophysical observation anomalies compared to the level before the 2021 Maduo MS7.4 earthquake, Qinghai Province, it is determined that the evaluation of earthquake trend in this area is between MS6-7. In November 2022, according to the "Technical Specification for Determining Annual National Critical Earthquake Risk Areas", based on the annual urgency determination results of long-term major earthquake risk sources, anomalous variation of gravity, seismic activity anomalies of a small earthquake, geophysical observation anomalies such as quasi synchronous changes of ground fluid, and comprehensive probability prediction results, it was comprehensively determined that there is a probability of an earthquake with MS6.0 or so occurring in the central and western sections of the Qilian Mountains seismic belt in 2022. In December 2022, there were new short-term ground fluid anomalies such as the water temperature at Delingha station and the escaped gas radon from groundwater at Xining station in the northeastern Qinghai-Tibet Plateau. Based on the short-term and imminent earthquake tracking technical solutions and analysis strategies in the Gansu-Qinghai region, the comprehensive earthquake prediction result was that there is a probability of an earthquake with MS6.0 or so occurring in the central and western sections of the Qilian Mountains seismic belt in January 2021.
How to cite: Li, G., Yu, H., Yang, W., and Yuan, Z.: Review of the Earthquake Prediction Process and Basis for the 2022 Menyuan MS6.9 Earthquake, Qinghai Province, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1239, https://doi.org/10.5194/egusphere-egu25-1239, 2025.
The Tatun Volcano Group (TVG) is an active volcano situated near a densely populated area with over 7 million residents. Given the existence of risk regarding volcanic activities, a dense seismic network has been deployed in the TVG by the Taiwan Volcano Observatory at Tatun. We used the observed seismic data to invert the yearly velocity model from 2014 to 2021. After a series of careful examinations, we constructed a 4D seismic velocity model in the TVG. Then we found the velocity model has the significant variations beneath the Dayoukeng where the helium isotope ratio (3He/4He) is approaching 7. Additionally, the area with significant variations of seismic wave velocity is located at the plausible pathway of volcanic fluids from deep to near surface in the TVG. Therefore, we consider that the temporal variations of velocity structures are associated with the local activities of volcanic fluids in the TVG.
How to cite: Pu, H.-C., Lin, C.-H., Lai, Y.-C., Shih, M.-H., and Lee, H.-F.: Temporal variations of velocity structure in the Tatun Volcano Group, Northern Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5443, https://doi.org/10.5194/egusphere-egu25-5443, 2025.
Earthquake induced ionospheric disturbances have become an important topic in earthquake prediction and monitoring research. On June 1, 2022, a magnitude 6.1 earthquake struck Ya'an, Sichuan, China. This study analyzes the changes in Total Electron Content (TEC) before and after the earthquake using GNSS (Global Navigation Satellite System) observational data, and investigates the ionospheric disturbances triggered by the earthquake and their possible mechanisms. We utilized GNSS station data from the Sichuan region to examine the TEC variations before and after the earthquake. The results reveal significant TEC anomalies within 150 km of the epicenter in the first hour following the earthquake, with a maximum change of up to 30% compared to the pre-earthquake background value. Notably, the TEC changes in the immediate vicinity of the epicenter showed a rapid increase followed by a swift decay, exhibiting clear temporal and spatial dependencies. Additionally, short-term ionospheric TEC fluctuations were found to correlate with atmospheric pressure changes. To further investigate the source of these disturbances, this study also combined meteorological and geomagnetic data observed during the earthquake. We found that the ionospheric disturbances might be closely related to the propagation of seismic-induced atmospheric pressure waves reaching the ionosphere. Furthermore, we applied numerical simulations to describe how these pressure waves could affect the ionospheric electron density, leading to changes in TEC. This study provides new empirical data on earthquake-induced ionospheric disturbances and reveals a possible coupling mechanism between earthquakes and the ionosphere. By integrating GNSS TEC data with meteorological and geomagnetic observations, this research offers new methods and theoretical support for ionospheric monitoring.
How to cite: Zhang, S.: Ionospheric Response to the 2022 Ya'an Earthquake in China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4753, https://doi.org/10.5194/egusphere-egu25-4753, 2025.
FORMOSAT7-COSMIC2 Mission is consist of six satellites equipped with GNSS radio occultation (RO) payload, in-situ ion density and velocity meters (IVM), and RF beacon transmitters at low latitudes. Signal-to-noise ratio (SNR) of RO soundings provides observations of irregularity altitudes, and IVM measures in-situ density fluctuations at satellite altitude of 550 km. Combining RO, IVM, ground-based receivers of beacon and GNSS, it is like an observation suite of plasma irregularities that provides unprecedented number of observations that were not available previously. The observation suite provides opportunity to monitor the variations of plasma irregularity structure and possibly be able to see their growth and subsidence. As the solar activity elevated to date, our observations show that seasonal irregularities occur more frequently with grater intensity. Meanwhile, as the magnetic storms also occur much more often with greater intensity, storm time variations of the irregularities become much more complex. In this presentation, we show that growth of strong low latitude plasma irregularities during storms and some of them last over the entire evening period. They are likely driven by the interplay of electric field and traveling ionospheric disturbances driven by magnetic storms. We will also present the dynamic irregularities driven by nature hazard events, such as earthquakes, tsunami and volcanos, from the observation suite which shows that the extreme event could lead to irregularity growth comparable to those driven by the space weather events. The recent results driven by 2022 Tonga volcano eruption is shown as the example.
How to cite: Lin, C., Rajesh, P. K., Hsiao, T.-Y., Lin, C.-Y., and Huang, C.-Y.: Study of the ionosphere responses to lithospheric activities using GNSS and FORMOSAT-7/COSMIC-2, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17871, https://doi.org/10.5194/egusphere-egu25-17871, 2025.
