Strong earthquakes and volcano eruptions generate atmospheric waves in the infrasound range that can reach ionospheric heights and cause electron density disturbances that can be monitor remotely, e.g., using electromagnetic waves. Using infrasound measurement in the ionosphere by continuous radio Doppler sounding in Europe, the differences between ionospheric disturbances induced by earthquakes and volcano eruption are discussed on the examples of the recent M=7.7 Turkey 6 February 2023 earthquake and Hunga eruption on 15 January 2022. It will be shown that the main difference is that co-seismic (induced by seismic waves) infrasound detected in the ionosphere propagated roughly vertically and is generated locally (below the observation in the ionosphere) by vertical movement of ground surface. On the other hand, the infrasound induced by volcano eruption propagated most probably from the source (volcano) and leaked to the ionosphere from the imperfect stratospheric and thermospheric wave guide. In addition, a distinct travelling ionospheric disturbance was observed.    

How to cite: Chum, J., Koucká, P., Šindelářová, T., and Rusz, J.: Differences between ionospheric infrasound induced by a strong volcanic eruption and an earthquake., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3553, https://doi.org/10.5194/egusphere-egu24-3553, 2024.

A solar storm can trigger severe geomagnetic and ionospheric disturbances, and activities originating from the Earth’s surface can do so as well. This presentation will introduce the sudden changes in the ionospheric plasma structure and electrodynamics after large lithospheric disturbances, such as earthquakes/tsunamis and volcanic eruptions. The main focus will be on the two significant events of the magnitude 9.0 Tohoku earthquake/tsunami (38.3°N 142.4°E) in the northeastern sea area of Japan on 11 March 2011, and the undersea volcanic eruption in Tonga (20.6°S 175.4°W), Central Pacific, on 15 January 2022. This presentation will also discuss the main characteristics of disturbances in ionospheric structures and electrodynamics. Investigating the two events enhances our comprehension of the sensitivity of the ionosphere response to lithospheric activities.

How to cite: Sun, Y.-Y.: Electrodynamic changes in the ionosphere due to large lithospheric disturbances, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4979, https://doi.org/10.5194/egusphere-egu24-4979, 2024.

Pre-earthquake anomalous phenomena in different geospheres have been widely reported.  Scientists found that the anomalies appear days to months prior to earthquakes from distinct geophysical parameters.  It is urgent and challengeable to investigate impending-earthquake anomalous signals for earthquake prediction.  The MVP-LAI (Monitoring Vibrations and Perturbations in the Lithosphere, Atmosphere, and Ionosphere) system was established at Leshan, Sichuan, China in 2021.  The system monitors the changes of over 20 various geophysical parameters from subsurface to ionosphere.  It aims to gain insights into the mechanisms of the lithosphere-atmosphere-lithosphere coupling (LAIC) during natural hazards.  On 5 September 2022, a M6.8 earthquake occurred at Luding, which is approximately 175 km from the MVP-LAI system.  The results show that the seven parameters from the MVP-LAI system simultaneously exhibited abnormal signal approximately 3 hours before the Luding earthquake. The parameters include ground tilts, air pressure, radon concentration, atmospheric vertical electric field, geomagnetic field, wind field, and total electron content. The enhancement in radon concentration suggests that the chemical channel could be a promising mechanism for the coupling of geospheres. On the other hand, air pressure, the geomagnetic field, and total electron content exhibit similar anomalous spectral characteristics. These anomalies may be attributed to atmospheric resonance before the earthquake. Furthermore, the reduction of the horizontal wind speed, and the increase of upward vertical wind support the resonance channel. The results demonstrate that the LAIC before earthquakes could be dominated by multiple potential mechanisms. The multi-parameter anomalies identified in this study guarantee approximately 3 hours of warning for people to prepare for the seismic event and mitigate hazards.

How to cite: Mao, Z. and Chen, C.-H.: Multi-parameter anomalies of the lithosphere, atmosphere, and ionosphere approximately three hours prior to the M6.8 Luding earthquake in China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7128, https://doi.org/10.5194/egusphere-egu24-7128, 2024.

In fair weather, the vertical atmospheric electric field is oriented downward (positive in the earth surface ordinate system) in the global atmospheric circuit. Some researchers revealed the unique phenomenon whereby once an upward vertical atmospheric electric field is observed in fair weather, an earthquake follows within 2-48 hours regardless of the earthquake magnitude. However, the mechanism has not been explained with a suitable physical model. In this paper, a physical model is presented considering four types of forces acting on charged particles in air. It is demonstrated that the heavier positive ions and lighter negative ions are rapidly separated. Finally, a reversed fair weather electrostatic field is formed by the above charge separation process. The simulation results have instructive significance for future observations and hazard predictions and it still needs further research.

How to cite: Chen, T. and Li, L.: Atmospheric charge separation mechanism due to gas release from the crust before an earthquake, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3308, https://doi.org/10.5194/egusphere-egu24-3308, 2024.

It is reported that earthquakes can trigger coseismic ionospheric disturbances, leading to the so called Lithosphere-atmosphere-ionosphere (LAI) coupling phenomenon. The acoustic-grave wave (AGW) is an important mechanism to induce such a phenomenon. In this study, we present a semi-analytic method to calculate AGWs excited by an earthquake source in the stratified lithosphere-atmosphere model and conduct numerical simulations to investigate characteristics of the AGWs. The results show that mainly two kinds of AGWs can be generated by the earthquake source. One is the head AGWs wave generated by the Rayleigh wave propagating along the surface, which propagates upwards nearly vertically. Another one is the epicenter AGWs generated by the direct seismic waves from the source. Both the head and epicenter AGWs are sensitive to the earthquake focal mechanism and are influenced by the structures of the atmosphere and solid earth. We also apply our method to a real earthquake event and compare the synthetic signals with the observed data.

How to cite: Gao, Y. and Li, T.: Acoustic-gravity waves generated by a point earthquake source, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3330, https://doi.org/10.5194/egusphere-egu24-3330, 2024.

In this study, we adopt a horizontally layered model which consisting of air, seawater and undersea porous rock and develop an analytically-based method to calculate the seismic and EM fields generated by undersea earthquakes. We conduct numerical simulations to investigate the characteristics of the EM response in three case (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. The first is the early EM wave arriving before the seismic waves and the second is the coseismic EM fields with apparent speed 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. We applied this method to simulating the EM response to the 2022 Mw 7.3 earthquake that took place in the sea near Fukushima, Japan. At the receiver with 80 km epicentral distance at the seafloor, the predicted coseismic electric and magnetic signals reach the amplitudes of 2 μV/m and 2 nT, respectively. The results suggest a possibility to monitor the EM disturbances associated with marine earthquakes and use them to serve the earthquake early warning or earthquake mitigation.

How to cite: Cheng, Q. and Gao, Y.: Electromagnetic response to undersea earthquakes in marine layered model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3948, https://doi.org/10.5194/egusphere-egu24-3948, 2024.

Based on the stratified lithosphere-atmosphere model, we present a semi-analytic method for calculating acoustic-gravity waves (AGWs) excited by a finite fault in the lithosphere. A finite fault is decomposed into a series of small subfaults, each treated as a point source with distinct rupture times. The fault is assumed to slide uniformly at a constant velocity along a specific direction. Simulation results reveal that both sides of the fault generate two types of AGWs when the fault rupture initiates and ceases. One type is the head AGW, generated by the P and Rayleigh waves propagating along the surface. The other one is the epicenter AGW, produced by direct seismic waves. The propagation of the AGWs is directional and related to the fault mechanism. We investigated a vertical strike-slip fault and a thrust fault, finding that the velocity amplitudes of the AGWs caused by both types of faults along the rupture direction are larger than the opposite direction. The AGWs induced by the thrust fault are stronger than those caused by the strike-slip fault. Furthermore, variations in the rupture velocity result in differences in waveform.

How to cite: Li, T. and Gao, Y.: Simulation of the atmospheric Acoustic-gravity waves caused by a finite fault, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2998, https://doi.org/10.5194/egusphere-egu24-2998, 2024.

Following the eruption of the Hunga Tonga-Hunga Ha'apai (hereafter called ‘Tonga’) volcano just before local sunset on 15 January 2022, satellite data reveals the formation of a large-scale plasma depletion surrounding the region. This depletion persisted for roughly 14 hours, until local sunrise resumed plasma production. By combining in-situ and remote satellite observations, we seek to characterize the depletion's magnitude, spatial scale, and temporal evolution in the hours following the eruption. We will compare this to observations of ionospheric holes following previous impulsive lower atmospheric events, such as the 2011 Tohoku earthquake. Finally, we will investigate the dominant mechanism for locally depleting the plasma following this event, considering field-aligned ion drag, cross B transport due to electric fields arising from dynamo or other effects, and changing recombination rates. We aim ultimately to better understand the coupling between the lower atmosphere and ionosphere/thermosphere system following impulsive events such as this eruption. 

How to cite: Gasque, C., Harding, B., Immel, T., Wu, Y.-J., and Triplett, C.: The case of the missing ionosphere: Investigating the ionospheric hole following the 2022 Tonga volcanic eruption, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12791, https://doi.org/10.5194/egusphere-egu24-12791, 2024.

The China Seismo-Electromagnetic Satellite (CSES), with a sun-synchronous orbit at 507 km altitude, was launched on 2 February 2018 to investigate seismo-ionospheric precursors (SIPs) and ionospheric space weather.  The CSES probes manifest longitudinal features of 4-peak plasma density and three plasma depletions in the equatorial/low-latitudes as well as mid-latitude troughs.  CSES plasma and the total electron content (TEC) of the global ionosphere map (GIM) are used to study PEIAs associated with a destructive M7.0 earthquake and its followed M6.5 and M6.3/M6.9 earthquakes in Lombok, Indonesia, on 5, 17, and 19 August 2018, respectively, as well as to examine ionospheric disturbances induced by an intense storm with the Dst index of -175 nT on 26 August 2018.  Spatial analyses of GIM TEC and CSES plasma quantities discriminate SIPs from global effects and locate the epicenter of possible forthcoming large earthquakes.  CSES ion velocities are useful to derive SIP- and storm-related electric fields in the ionosphere.

How to cite: Liu, J.-Y., Chang, F.-Y., Wen, Y.-C., and Shen, X.: Ionospheric space weather and seismo-ionospheric precursors observed by China seismo-electromagnetic satellite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4579, https://doi.org/10.5194/egusphere-egu24-4579, 2024.

On St. Patrick's Day, March 17, 2015, the first historical intense geomagnetic storm (Dst < −200 nT) of the 24^th solar cycle occurred. This storm caused complex effects around the globe. Geomagnetic storms are a concern for society, especially the strongest storms and how they affect satellite communications, navigations and power grids. Using Global Positioning System (GPS) data to compute the Total Electron Content (TEC) of the Earth's ionosphere is one of the most common methods used to investigate perturbations in the ionosphere. GPS TEC variations may reveal ionospheric anomalies, which might endanger the continuity and availability of GPS performance metrics. Thus, the ionospheric consequences of geomagnetic storms have been researched intensively for decades but are still not fully understood. This study investigates the ionospheric behaviour during an intense geomagnetic storm that occurred from 14 - 24 March 2015. In particular, we used geomagnetic indices and GPS TEC data from various IGS stations all over the world to give a comprehensive analysis of how the ionospheric total electron content changes in both the northern and southern hemispheres at different latitude and longitude stations.

How to cite: Malvi, B. and Purohit, P.: Global Ionospheric Responses in Both Hemispheres during the 2015 St. Patrick’s Day Storm, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-509, https://doi.org/10.5194/egusphere-egu24-509, 2024.

The sudden cutoff of solar radiation caused by the solar eclipse could cause significant changes in the thermosphere and ionosphere, considering the fact that the solar radiation plays a significant role in their dynamical processes. In this study, the thermospheric neutral wind recorded by the Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) on the Ionospheric Connection Explorer (ICON) spacecraft and metero radar were analyzed to examine the variations in thermospheric wind during and after the 21 June 2020 annular solar eclipse over the East China area. The neutral wind observations showed direct evidences that the solar eclipse disturbed the mesosphere and low thermosphere for more than 10 hours. The clear enhancement of the meridional wind during the moon obscuration and sharply decreased meridional wind after local sunset suggested that a large-scale oscillation was caused by the solar eclipse, which persisted from daytime to nighttime.

How to cite: Wang, J. and Sun, Y.-Y.: Thermospheric wind response to the annular solar eclipse on 21 June 2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2968, https://doi.org/10.5194/egusphere-egu24-2968, 2024.

Taiwan is situated in the collision zone between the Philippine Sea Plate and the Eurasian Plate, where these two plates are converging at an average rate of 8.2 centimeters per year, leading to significant crustal deformation on the island. Utilizing data from GPS (Global Positioning System) measurements processed and analyzed using Bernese software, the average velocity field of crustal movements can be estimated, providing a more comprehensive understanding of crustal deformation. The combination of GPS and seafloor geodesy observations can aid in unraveling the seismic processes along plate boundaries. Due to the inability of GPS signals to penetrate seawater, acoustic methods are employed to make ocean bottom pressure (OBP) measurements, serving as a valuable and unique tool for monitoring integrated ocean currents and observing sea level changes.

OBP measurements have been applied for various geophysical purposes, including ocean physics and marine geodesy. Seafloor Absolute Pressure Gauges (SAPG) based on quartz oscillation principles have been employed to record phenomena such as tsunamis, ocean tides and non-tidal sea level variations, as well as seafloor vertical deformations. These instruments play a crucial role in marine physics research.

In recent years, the Academia Sinica has also conducted research in the surrounding waters of Taiwan using acoustic positioning methods for seafloor geodetic observations. In conjunction with seafloor geodetic observations, ocean bottom pressure (OBP) measurement is another method employed.

The seafloor absolute pressure gauge (SAPG) developed by the Academia Sinica is composed of a Paroscientific Inc. quartz vibrating pressure sensor, integrated with an OEM data logger from RBR-Global Co. (http://www.rbr-global.com/products/bpr) and components such as the BART Boards with Regular Tuning ROUND and Acoustic Transducer that made by EdgeTech Co. The assembly of SAPG has been completed, and it has been deployed in the waters off the eastern coast of Taiwan for long-term observations. This paper will introduce the instrument assembly of SAPG, pre-deployment testing, and preliminary analysis results of the marine data.

How to cite: Lin, C.-R., Hsu, Y.-J., Lin, F.-S., and Chang, K.-H.: Design, Testing, and Preliminary Data Analysis of the Seafloor Absolute Pressure Gauge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3089, https://doi.org/10.5194/egusphere-egu24-3089, 2024.

Typhoon is a key dynamic factor triggering landslides. In view of the fact that the previous susceptibility evaluation models rarely consider the interaction between typhoon and static factors, carry out research on the optimal dynamic and static factors combination of typhoon-induced landslides susceptibility. Using the interpretability of machine learning, the importance ranking of dynamic and static factors is carried out to identify key impact factors. On this basis, the importance of static factors under the influence of typhoon is compared, and the interaction between typhoon and static factors is analyzed. Finally, the optimal combination of dynamic and static factors is proposed by using k-fold cross-validation method and taking the average descent accuracy as the index. The results show that the importance of the key influencing factors of typhoon-induced landslide from high to low mainly includes: elevation, NDVI, road and other factors; the addition of typhoon and rainstorm factors significantly increased the importance of factors susceptible to typhoon, such as water system and vegetation, with an increase rate of 24.8-151.7 %. The optimal dynamic and static factors combination of typhoon rainstorm landslide includes all key static factors and four dynamic factors, among which the dynamic factors are: maximum sustained wind speed, rainfall, distance from typhoon center and near gale wind circle radius. The results of ROC curve verification show that the selection of the optimal factor combination can increase the accuracy of the evaluation model by 1.5%-3.5%, which can significantly improve the accuracy and rationality of the susceptibility mapping of typhoon-induced landslides.

Keywords: Impact factor, Typhoon, Landslides susceptibility, Interpretability of machine learning.

How to cite: Wang, F., Zhou, L., Liu, Y., and Chen, F.: Optimal factor combinations selection in typhoon-induced landslides susceptibility mapping using machine learning interpretability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16885, https://doi.org/10.5194/egusphere-egu24-16885, 2024.

Radio diagnostics, including scattering of electromagnetic waves (EMW) by spatiotemporal disturbances of the ionospheric plasma in the ELF (Extremely Low Frequencies, Hz), VLF (Very Low Frequencies, kHz), HF (High Frequencies, MHz) and microwaves (GHz) ranges, is one of the most effective methods for detecting and studying extreme modifications of ionospheric “space weather”. Such modifications are caused, in particular, by influences “from above” (from the Solar wind and magnetospheric storms) and “from below” (from tropical cyclones, earthquakes and volcanoes) and other Natural Hazards. Such ionospheric modifications are manifested, in particular, in the excitation of TIDs (Traveling Ionospheric Disturbances) and scintillations on various scales of the HF waves detected by LOFAR (Low Frequency Array) Radio Telescope.

In combination with other ionosphere sounding techniques (as GNSS) LOFAR can give a complementary insight to the ionospheric structures. We present LOFAR scintillation observations compared with GNSS-observed ionospheric irregularities in order to assess the ionospheric plasma structures. Classified ionospheric scintillation data will be presented. These include quasi-periodic, quasi-pulse, flare-like and other disturbances detected on the LOFAR radio telescopic systems in Poland, Great Britain, Germany and other countries. Spectral processing of LOFAR data is currently being carried out to identify various types of ionospheric disturbances, including TIDs, that characterize ionospheric space weather. We are currently developing TID modelling methods aimed at comparison with experimental data. Theoretical and experimental data on ionospheric disturbances associated with the eruption of the Hunga-Tonga-Hunga-Ha'apai volcano in January 2022 are presented and the results of their comparison are discussed. Based on the data-driven approach, effective current sources associated with lightning discharges caused by the eruption of the Hunga-Tonga-Hunga-Ha'apai volcano are identified in the ULF (Ultra-Low Frequency), ELF and VLF ranges. In particular, theoretical results are given on: (i) the excitation of the first and second modes of the Schumann resonator; (ii) the fundamental possibility of simultaneous excitation of coupled global Schumann and local Alfvén resonators. The results of applying the model for the scattering of HF electromagnetic waves (EMWs) on ionospheric disturbances such as increased and decreased plasma densities will be presented. The effects of birefringence, the dependence of EMW frequency on time in moving plasma, diffraction and dispersion of EMWs will be included, based on the advanced method of Complex Geometrical Optics.

An information is provided on the Ukrainian Ground-Based Space Weather Monitoring Network. This network includes GNSS stations, VLF receivers, Magnetotelluric stations, Ionosonde and magnetometer INTERMAGNET. Examples of corresponding measurements are presented.

Yu.R. and L.B. are grateful, for partial funding this research, by National Science Centre, Poland, grant No 2023/49/B/ST10/03465, “Modern Radio-Diagnostics of the Ionosphere using LOFAR and GNSS Data”

How to cite: Rapoport, Y., Grimalsky, V., Krankowski, A., Błaszkiewicz, L., Flisek, P., Kotulak, K., Fron, A., Reshetnyk, V., Grytsai, A., Ivchenko, V., Liashchuk, A., and Petrishchevskii, S.: Experimental data and models for radio diagnostics of extreme impacts “from above” and “from below” on ionospheric space weather: VLF, LOFAR and GNSS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13179, https://doi.org/10.5194/egusphere-egu24-13179, 2024.

The Tonga-Kermadec zone stands out as one of the most active areas in the world for continuous subduction processes characterizing the area. In the recent few years, it has been affected by two important geophysical events: first a strong earthquake of M7.2 on June 15, 2019, with the epicentre in Kermadec Islands (New Zealand), and then an exceptional eruption of Hunga Tonga-Hunga Ha’apai volcano on January 15, 2022. We focused our attention on the phenomena appearing before, during and soon after each event, employing a multi-parametric and multi-layer approach in order to analyse the geodynamics of the entire area and the involved lithosphere-atmosphere-ionosphere coupling (LAIC). In details, for the lithosphere we conducted a seismic analysis of the earthquake sequence culminating with the mainshock on June 15, 2019, and of those preceding the big eruption, within a circular area with Dobrovolsky strain radius corresponding to that of an equivalent seismic event of magnitude equal to the energy released during the eruption. Moving to the atmosphere, we considered some parameters possibly influenced by seismic and volcanic events, using the CAPRI algorithm to the ECMWF datasets to detect anomalies in their values. Finally, by observing satellite data, we analysed the magnetic field and electron burst precipitations, potentially correlated to the events. All these observations, along with their similarities and differences, provide a better insight of the complex tectonic context.

How to cite: D'Arcangelo, S., Regi, M., De Santis, A., Perrone, L., Cianchini, G., Soldani, M., Piscini, A., Fidani, C., Sabbagh, D., Lepidi, S., and Di Mauro, D.: Comparative analysis of recent seismic and volcanic events in the Tonga-Kermadec zone: Insights into Lithosphere-Atmosphere-Ionosphere Coupling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11811, https://doi.org/10.5194/egusphere-egu24-11811, 2024.