NH10.5 | Impact of natural hazards on lithosphere, atmosphere, and space
EDI
Impact of natural hazards on lithosphere, atmosphere, and space
Co-organized by AS4/ESSI4/GI4
Convener: Chieh-Hung Chen | Co-conveners: Yen-Jung Wu, Yasuhide Hobara, Gilbert PiECSECS, Min-Yang ChouECSECS
Orals
| Tue, 16 Apr, 08:30–12:25 (CEST)
 
Room 1.14
Posters on site
| Attendance Tue, 16 Apr, 16:15–18:00 (CEST) | Display Tue, 16 Apr, 14:00–18:00
 
Hall X4
Posters virtual
| Attendance Tue, 16 Apr, 14:00–15:45 (CEST) | Display Tue, 16 Apr, 08:30–18:00
 
vHall X4
Orals |
Tue, 08:30
Tue, 16:15
Tue, 14:00
Natural hazards in the Earth system, such as earthquakes, tsunamis, landslides, volcanic eruptions, cyclones, and extreme weather, primarily brew and occur in the lithosphere and troposphere, which often happen unexpectedly and impact human daily life. Tracing the atmospheric and ionospheric disturbances due to the hazards benefits nowcasting their occurrences. On the other hand, solar activities can induce geomagnetic storms that accompany the magnetosphere-ionosphere coupling and atmospheric disturbances, which impact satellite operation, global high-precision positioning and navigation, and damage the electric supply system near the Earth’s surface. Impacts of the hazards are not limited to a specific geosphere but often impact multiple geospheres, subsequently affecting daily life. Therefore, there is an urgent need for instrumental arrays to monitor useful signals, novel methodologies to retrieve associated data, and numerical simulations to understand the interaction between the lithosphere (hydrosphere), atmosphere, and space (LAS).

In this session, we invite scientists interested in studying the interaction between the lithosphere (hydrosphere), atmosphere, and space but it is not limited to natural hazards alone. The interaction between the multiple geospheres can be excited by numerous potential sources, ranging from lithospheric activities in the Earth’s interior to solar activities in the space beyond the Earth system. Observations of parameters in one geosphere interacting with others, methodologies for detecting signals related to changes in the other geospheres, and the construction of numerical models spanning multiple geospheres are all welcome. The session aims to integrate scientists studying distinct fields to improve and enhance our understanding of the LAS interactions. Ultimately, this research aims to mitigate the loss of human life and property coming with a higher risk of being affected by natural hazards from the Earth and space.

Orals: Tue, 16 Apr | Room 1.14

Chairpersons: Chieh-Hung Chen, Yang-Yi Sun
08:30–09:00
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EGU24-3553
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solicited
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On-site presentation
Jaroslav Chum, Petra Koucká, Tereza Šindelářová, and Jan Rusz

 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.

09:00–09:10
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EGU24-4979
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On-site presentation
Yang-Yi Sun

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.

09:10–09:20
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EGU24-7128
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ECS
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On-site presentation
Zhiqiang Mao and Chieh-Hung Chen

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.

09:20–09:30
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EGU24-3308
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On-site presentation
Tao Chen and Lei Li

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.

09:30–09:50
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EGU24-3330
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solicited
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On-site presentation
Yongxin Gao and Ting Li

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.

09:50–10:00
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EGU24-3948
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ECS
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On-site presentation
Qianli Cheng and Yongxin Gao

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.

10:00–10:10
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EGU24-2998
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ECS
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On-site presentation
Ting Li and Yongxin Gao

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.

Coffee break
Chairpersons: Yongxin Gao, Gilbert Pi, J. Y. Liu
10:45–11:15
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EGU24-12791
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solicited
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On-site presentation
Claire Gasque, Brian Harding, Thomas Immel, Yen-Jung Wu, and Colin Triplett

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.

11:15–11:25
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EGU24-4579
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On-site presentation
Jann-Yenq Liu, Fu-Yuan Chang, Yun-Cheng Wen, and Xuhui Shen

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.

11:25–11:35
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EGU24-509
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ECS
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Virtual presentation
Bhupendra Malvi and Pramod Purohit

On St. Patrick's Day, March 17, 2015, the first historical intense geomagnetic storm (Dst < −200 nT) of the 24th 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.

11:35–11:45
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EGU24-2968
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On-site presentation
Jin Wang and Yang-YI Sun

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.

11:45–11:55
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EGU24-3089
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ECS
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On-site presentation
Ching-Ren Lin, Ya-Ju Hsu, Feng-Sheng Lin, and Kun-Hui Chang

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.

11:55–12:05
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EGU24-16885
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On-site presentation
Fei Wang, Liwei Zhou, Yanlin Liu, and Fei Chen

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.

12:05–12:15
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EGU24-13179
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Virtual presentation
Yuriy Rapoport, Volodymyr Grimalsky, Andrzej Krankowski, Leszek Błaszkiewicz, Paweł Flisek, Kacper Kotulak, Adam Fron, Volodymyr Reshetnyk, Asen Grytsai, Vasil Ivchenko, Alex Liashchuk, and Sergei Petrishchevskii

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.

12:15–12:25
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EGU24-11811
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ECS
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Virtual presentation
Serena D'Arcangelo, Mauro Regi, Angelo De Santis, Loredana Perrone, Gianfranco Cianchini, Maurizio Soldani, Alessandro Piscini, Cristiano Fidani, Dario Sabbagh, Stefania Lepidi, and Domenico Di Mauro

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.

Posters on site: Tue, 16 Apr, 16:15–18:00 | Hall X4

Display time: Tue, 16 Apr 14:00–Tue, 16 Apr 18:00
Chairpersons: Yasuhide Hobara, Min-Yang Chou, Chieh-Hung Chen
X4.85
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EGU24-4806
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solicited
Cheng-Horng Lin, Min-Hung Shih, and Ya-Chuan Lai

The powerful acoustic waves generated by the major eruption on January 15, 2022 on Hunga Tonga Hunga Ha’apai (HTHH) of Tonga were unambiguously recorded in Taiwan by several infrasonic stations and Formosa array, which consists of 146 broadband seismic stations with an average spacing of ~5 km in northern Taiwan. Based on the carefully analyses of the broadband frequency-wavenumber method (BBFK) and the Fast Fourier Transform (FFT), it was interesting to see that both data sets consistently showed a resonant frequency of ~0.0117 Hz persisted for more than 25 minutes after the first major eruption. Such a long-duration resonance of the remote seismo-acoustic waves provides a rapid estimation of the erupted magma volume of 0.215 ± 0.015 if the volcanic cavity produced by the erupting magma is considered as a classic Helmholtz resonator. Thus, we may obtain that the first major eruption alone of HTHH rated a 4 on the VEI scale. But the total erupted volume could reach up VEI 5 or even 6 if we consider all of the accumulated magma from the following eruptions.

How to cite: Lin, C.-H., Shih, M.-H., and Lai, Y.-C.: Rapid Estimation of 2022 Tonga Erupted Volume from the Remote Seismo-Acoustic Resonance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4806, https://doi.org/10.5194/egusphere-egu24-4806, 2024.

X4.86
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EGU24-2698
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solicited
Chieh-Hung Chen, Yang-Yi Sun, Kai Lin, and Xuemin Zhang

The Monitoring Vibrations and Perturbations in the Lithosphere, Atmosphere, and Ionosphere (MVP-LAI) instrumental array was established in Sichuan, China, in 2021. The MVP-LAI station has demonstrated its efficacy in investigating the causal mechanisms of LAI coupling among multiple geophysical parameters in the vertical direction above a specific area on the Earth's surface during natural hazards such as earthquakes, volcanic eruptions, and landslides. Another MVP-LAI station will be established in Yunnan, approximately 200 km away from the first one, this year. Additionally, a high-frequency Doppler sounder array, comprising two transmitters with distinct frequencies and eight receivers, will be installed in areas covering both MVP-LAI stations to monitor vertical changes in ionospheric layers at two specific altitudes. It is noteworthy that observations from seismometers, magnetometers, and ground-based GNSS receivers in this area can be utilized to capture waves and/or perturbations propagating along the horizontal layer at the Earth's surface, at altitudes of approximately 100 km and 350 km, respectively. The two frequencies employed by the high-frequency Doppler sounder array can aid in comprehending how waves and/or perturbations propagate along the horizontal layers at approximately 200 km and 250 km in altitude. When the two MVP-LAI stations, the high-frequency Doppler sounder array, and substations are integrated, vibrations and/or perturbations propagate both vertically and along the five horizontal layers, even in slant directions, can be detected. The collaboration between MVP-LAI stations and horizontal observations forms the Greater Omnidirectional Ascertain Technology (GOAT), which enhances the understanding of the proportional mechanism for the LAI coupling.

How to cite: Chen, C.-H., Sun, Y.-Y., Lin, K., and Zhang, X.: Greater Omnidirectional Ascertain Technology (GOAT) of the Monitoring Vibrations and Perturbations in the Lithosphere, Atmosphere, and Ionosphere (MVP-LAI) Array, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2698, https://doi.org/10.5194/egusphere-egu24-2698, 2024.

X4.87
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EGU24-2380
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ECS
|
solicited
Min-Yang Chou, Jia Yue, Nicholas Pedatella, Sarah McDonald, and Jennifer Tate

Large-scale wave structure (LSWS) in the bottomside F layer is pivotal in developing equatorial plasma bubbles (EPBs), potentially serving as a precursor of EPBs. Gravity waves, hypothesized to contribute through the wind dynamo mechanism, face experimental challenges. This study, utilizing the coupled SAMI3 and SD-WACCM-X models, investigates the role of gravity wave wind dynamo effect and gravity in LSWS development. We found that the gravity waves originating from the lower atmosphere induce vertical E×B drift perturbations in the nighttime ionosphere. Notably, LSWS can manifest independently of gravity, emphasizing the dominance of the gravity wave wind dynamo mechanism. However, LSWS exhibits more pronounced vertical E×B drift perturbations, indicating an additional eastward Pedersen current driven by equatorial winds (i.e., downward wind) via the gradient drift instability. Gravity-driven Pedersen current, therefore, plays a role in amplifying the LSWS and EPB development. Simulations also show the emergence of pre-dawn turbulent bubble-like irregularities in the bottomside ionosphere even without gravity, attributed to concentric gravity waves over the magnetic equator. Our findings underscore the significant influence of gravity waves on the formation of LSWS and ionospheric irregularities.    

How to cite: Chou, M.-Y., Yue, J., Pedatella, N., McDonald, S., and Tate, J.: Modeling Equatorial Plasma Bubbles with SAMI3/SD-WACCM-X: Large-Scale Wave Structure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2380, https://doi.org/10.5194/egusphere-egu24-2380, 2024.

X4.88
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EGU24-2985
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solicited
Chi-Kuang Chao

A FORMOSAT-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 6 years.  In this poster, global plasma density irregularities in the pre-midnight sector had been seasonally selected from FORMOSAT-5/AIP data during 2018 to 2023.  Yearly variations of these irregularity patterns with solar cycle could be clearly observed.

How to cite: Chao, C.-K.: Equatorial Plasma Density Irregularities Observed by Advanced Ionospheric Probe Onboard FORMOSAT-5 Satellite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2985, https://doi.org/10.5194/egusphere-egu24-2985, 2024.

X4.89
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EGU24-17238
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solicited
Yasuhide Hobara, Mako Watanabe, Mio Hongo, Hiroshi Kikuchi, Takuo Tsuda, and Masashi Hayakawa

In this paper, we report on the Atmospheric Electric Field (AEF) anomalies immediately before and after earthquakes (within 12 hours) in Japan. We demonstrate the results of a case study for several earthquakes that occurred close to our AEF observation network (within 100-200 km of the epicenter) under relatively fair local weather conditions. We found the common features for different earthquakes at different field sites e.g. 20~90 min period of clear anomalous signatures in wavelet spectrograms within a few hours around the main shock. Clear arrival time differences between AEF stations indicate propagating nature of observed AEF anomaly and enable us to calculate the propagation velocities and its occurrence timing. The observational results are compared with the dispersion relation of Internal Gravity Waves (IGW). Moreover, statistical results of the occurrence rate of the AEF anomalies support above mentioned results. Above-mentioned results may indicate the Lithosphere-Atmosphere Coupling, and we propose the physical mechanism of the observed electric field anomalies considering IGW originating from the epicenter region propagating over the field site and disturbing the local atmospheric electric field. 

How to cite: Hobara, Y., Watanabe, M., Hongo, M., Kikuchi, H., Tsuda, T., and Hayakawa, M.: Anomalous Atmospheric Electric Field Just around the Time of Earthquakes: Case and statistical studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17238, https://doi.org/10.5194/egusphere-egu24-17238, 2024.

X4.90
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EGU24-1054
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ECS
Bijoy Dutta and Javed N Malik

Disastrous earthquakes are a permanent threat to every second resident of our planet causing a massive loss of lives and property. Understanding the nature of earthquake precursory signatures and related hazard mitigation has immense potential for scientific advancement as well as for societal benefits. To study these multidisciplinary and complicated precursory signatures, several models have been proposed in favor of the Lithosphere- Atmosphere- Ionosphere- Coupling (LAIC) mechanism by earlier workers. The major objective of this study is to investigate the short-term perturbations in land surface temperature (LST), atmospheric air temperature (AT), atmospheric relative humidity (ARH), and in ionospheric vTEC prior to the destructive shallow sheeted Turkey-Syria earthquake (Mw 7.8, Depth 10 Km, Intensity IX) on 6th February 2023 and its major aftershocks (Mw 7.5, 6.8, 6, 6). Earthquakes of such large magnitude causes synchronization changes, not only in the atmospheric parameters but also in the ionospheric TEC. The GPS and GNSS (IGS) derived ionospheric TEC data are now being used extensively to investigate seismo-ionospheric perturbations over and near the epicentral regions of earthquakes over the last two decades. To identify the perturbation in the LST and atmospheric parameters (AT and RH), we have studied the spatio-temporal variation of MODIS (Terra) derived LST data and MERRA 2 (NASA) derived atmospheric temperature and relative humidity at 2 meter height. The Terra-MODIS derived LST differential time series reveals a prominent increase ~ 6-16 ⁰C from 18th to 26th Jan, 2023 around the epicentral region. Moreover, the hourly varying atmospheric parameters (AT, RH) have shown significant and synchronous deviations from 18th Jan to 26th Jan. The highest positive (+ve) deviation in the AT is found to be 10.33 ⁰C and the lowest negative (-ve) anomaly in the RH is found to be 45.67% on 19th Jan. The observed atmospheric anomalies are identified with respect to the constructed bounds using past 5 years hourly data (m ± 2σ). The temporal variation of ionospheric vTEC of the nearest grid point, derived from both GNSS (IGS) and GPS receivers shows a series of prominent –ve anomalies from 25th Jan to 1st Feb about 5-12 days prior to the main shock. After ruling out possible contributions due to the solar terrestrial environment with respect to F10.7 Scale and Ap index, it is found that the evolved TEC anomaly is seismogenic in origin. In order to visualize the TEC anomaly in spatio-temporal domain, we have plotted 2D latitude-longitude time (LLT) maps of different epochs during those anomalous days (Max anomaly~ -15 TECu on 28th Jan at UTC 11th and 12th hour). Considering the nearest plate boundary, spatial extent of TEC conjugates and TEC gradient we have determined the probable epicenter which showed very promising correlation in comparison to actual epicenter. This multi parametric spatio-temporal analysis of the pre-seismic signature will produce some beneficial insight to understand the LAIC mechanism in detail and somehow be able to save so many lives.

How to cite: Dutta, B. and Malik, J. N.: Potential Utilization of Multi-Parametric Earthquake Precursory Signatures in Support of LAIC Mechanism: A case study on Turkey- Syria Earthquake (6th Feb, 2023)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1054, https://doi.org/10.5194/egusphere-egu24-1054, 2024.

X4.91
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EGU24-7628
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ECS
The three-dimensional co-seismic and co-tsunami ionospheric perturbations related to the 2011 M9.0 Tohoku earthquake in Japan
(withdrawn)
Rui Song, Katsumi Hattori, Xuhui Shen, and Jann-Yenq Liu
X4.92
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EGU24-14108
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ECS
Huan Rao and Chieh-Hung Chen

The M7.8 and M7.5 earthquakes that occurred on 6 February 2023 in Turkey caused co-seismic ionospheric disturbances, and ionospheric total electron content (TEC) disturbances can be detected by Beidou geostationary satellites. The 17 GNSS continuous observation stations from IGS Net around the epicenters receive electromagnetic wave signals emitted by two Beidou geostationary satellites located above the equator at a frequency of 1 Hz. That allows us to obtain the TEC time series at fixed ionospheric piercing points (IPPs). Disturbances triggered by the M7.5 earthquake propagate farther and have a larger amplitude in general traveling at least 1600 km northwest and 800 km south and reaching the furthest area of the study with the maximum amplitude of about 2.5 TECU. For Mw 7.8 earthquake, the disturbances can be observed about 800 km northwest of the epicenter while no significant disturbances detected further away and the maximum amplitude of the disturbances is about 0.25 TECU. The TEC disturbances propagation speeds corresponding to the M7.5 and M7.8 earthquakes are 2.77 km/s and 2.60 km/s as the results of least squares fitting performed on epicentral distances and travelling times of the disturbances with the greatest amplitude. The speeds are closer to Rayleigh waves velocity of about 3 km/s at the surface rather than acoustic waves velocity of about 1 km/s in the ionosphere. The velocity of propagation for the co-seismic ionospheric disturbances, as determined by utilizing the Beidou geostationary satellites during two earthquakes, is consistent with that of the Rayleigh waves determined from the seismometers. Meanwhile, the velocity exhibits directional disparities for M7.5 earthquake.

How to cite: Rao, H. and Chen, C.-H.: Co-seismic ionospheric total electron content disturbances of Turkey earthquake doublet in 2023 detected by Beidou geostationary satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14108, https://doi.org/10.5194/egusphere-egu24-14108, 2024.

X4.93
|
EGU24-12565
Lucia Santarelli, Valentina Bruno, Igino Coco, Sofia De Gregorio, Paola De Michelis, Fabio Giannattasio, Paolo Madonia, Michael Pezzopane, Marco Pietrella, Massimo Rossi, and Roberta Tozzi

The TROPOMAG project investigates the possible effects of changes of the Earth’s magnetic field on the atmosphere and weather conditions with the aim to better quantify the natural sources of the atmospheric variability. This need raises to assess the observed climate trends more correctly, with a consequent better understanding of manmade effects on climate. Specifically, this work explores possible connections between atmospheric pressure anomalies and the occurrence of geomagnetic storms. To accomplish this task pressure data, recorded over some Italian volcanic areas, are analysed according to different methods and considering geomagnetic indexes. This work describes and discusses corresponding preliminary results.

How to cite: Santarelli, L., Bruno, V., Coco, I., De Gregorio, S., De Michelis, P., Giannattasio, F., Madonia, P., Pezzopane, M., Pietrella, M., Rossi, M., and Tozzi, R.: TROPOMAG - Influence of geomagnetic storms on the TROPOsphere dynamics: Can the Earth’s MAGnetic field be considered a proxy of climate changes? Some results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12565, https://doi.org/10.5194/egusphere-egu24-12565, 2024.

X4.94
|
EGU24-9414
Huiru Xu, Yuan Liang, Yiming Lai, and Guomin Li

The Qinling Orogenic Belt (QOB) is one of the most important orogens in Eastern Asia formed by the collision between the North China Block (NCB) and the South China Block (SCB). The evolution history of the QOB is essential to the assembly processes of the major blocks in China and the evolution history of the Proto-Tethys Ocean (Shangdan Ocean). Paleomagnetism can quantitatively restore the paleo-position of blocks, which is key to studying the related tectonic evolution. Hindered by the complex tectonic process, few paleomagnetic results have been reported from the QOB. Here we reported a primary paleomagnetic study from the northern QOB by conducting both rock magnetic and paleomagnetic experiments on the early Devonian Lajimiao pluton (~413Ma) in the North Qinling belt (NQB), to constrain its paleo-position and the evolution of the QOB during the early Paleozoic period.

253 cores from 28 sites were drilled by portable gasoline drills, and oriented by a magnetic compass and also a sun compass if possible. Rock magnetic experiments indicate that the main magnetic mineral in most of the samples is mainly magnetite in a pseudo-single domain or multi-domain state. Both thermal demagnetization and alternating-field demagnetization were applied to obtain the characteristic remanent magnetization. The Fisher-mean direction of the low-temperature/coercivity component is roughly consistent with the present geomagnetic field (PGF), suggesting that it is probably a viscous remanent magnetization caused by the PGF. The high-temperature/coercivity component yielded a Fisher-mean direction Ds/ Is = 355.8°/19.1° in stratigraphic coordinates, corresponding to a paleomagnetic pole of 65.8°N/299.9°E (A95=2.4°). It is the first Devonian paleomagnetic pole among the scarce paleomagnetic results from the QOB. This pole indicates that the NQB may have been located at a low latitude at the early Devonian, probably in proximity to both the North China and South China blocks. However, the difference between the coeval paleomagnetic poles from the three blocks (NQB, NCB, SCB) may hint the assembly process of the several major blocks is not simple and direct. Anyway, the newly obtained paleomagnetic pole from the NQB would be able to refine our understanding of the tectonic evolution of the QOB and the Proto-Tethys Ocean.

How to cite: Xu, H., Liang, Y., Lai, Y., and Li, G.: Primary Devonian paleomagnetic results from the Qinling orogenic belt and its implication for the evolution of the Proto-Tethys Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9414, https://doi.org/10.5194/egusphere-egu24-9414, 2024.

X4.95
|
EGU24-7281
|
ECS
Unbound geodesic orbit in the spacetime of charged black hole under higher derivative gravity
(withdrawn)
Yuhao Cui, Kai Lin, and Yang-Yi Sun
X4.96
|
EGU24-4922
Hsin-Chieh Pu, Cheng-Horng Lin, Hsiao-Fen Lee, Ya-Chuan Lai, Min-Hung Shih, Guo-Teng Hong, and Po-Tsun Lee

We analyzed 3,330 earthquake focal mechanisms and the fumarolic gases in the Tatun Volcano Group (TVG) during 2018–2021. Between June/2020 and June/2021, we found a concealed inflation beneath a depth of 2 km. We indicate this inflating mechanism was associated with the feeding volcanic fluids, which induced the past inflating cases in the TVG before 2018. We deliberated about the feeding features regarding this and the past cases and purpose three indicators to monitor such concealed activities, including the inflating indicator associated with the behaviors of earthquake faulting, heating indicator determined by the systematically high HCl/CO2 ratios, and discharging indicator displayed by the lasting high St/CO2 ratios. Using these indicators, we concluded that it was not rare during the last one decade that the concealed activities whose volcanic fluids were discharged occasionally.

How to cite: Pu, H.-C., Lin, C.-H., Lee, H.-F., Lai, Y.-C., Shih, M.-H., Hong, G.-T., and Lee, P.-T.: Indicators of the Activity Associated with Concealed Feeding Volcanic Fluids in the Tatun Volcano Group, Northern Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4922, https://doi.org/10.5194/egusphere-egu24-4922, 2024.

X4.97
|
EGU24-8677
Pengyu Zhang and Yang-Yi Sun

The ionosphere owns a complex electric current system mainly driven by the ionospheric electric field and thermospheric wind. Changes in current can generate geomagnetic signals that can be observed both on the ground and in space. In this study, we analyzed the ionospheric current in the Asia-Oceania region by utilizing geomagnetic data collected from magnetometers of ground-based observatories and SWARM satellites at ~450 km altitude. The results present the geomagnetic variations at the two distinct altitudes, encompassing longitudinal, latitudinal, and seasonal variations. Furthermore, the Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) was employed to simulate the associated geomagnetic signals. This study is the first to combine dense geomagnetic data from multiple altitudes and simulations to understand the ionospheric current in the Asia-Oceania region. The differences between the observational geomagnetic signals at different altitudes, along with the simulations, reveal a unique current structure that has not been previously discovered. The findings provide a new understanding of the intricate evolution of the current systems, which contributes to our knowledge of the electric dynamics within Earth's ionosphere.

How to cite: Zhang, P. and Sun, Y.-Y.: A unique structure of the ionospheric current over the Asian-Oceania region determined by the combination of the ground-based and space-borne magnetometers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8677, https://doi.org/10.5194/egusphere-egu24-8677, 2024.

Posters virtual: Tue, 16 Apr, 14:00–15:45 | vHall X4

Display time: Tue, 16 Apr 08:30–Tue, 16 Apr 18:00
Chairpersons: Strong Wen, Yen-Jung Wu
vX4.13
|
EGU24-14234
Strong Wen, Yulien Yeh, and Kuan-Ting Tu

There are many types of natural disasters in the world, among which earthquakes are sudden and highly uncertain, which may cause direct or indirect disasters, resulting in casualties, property losses, and infrastructure damage. Local seismic hazard analysis has been studied for a long time. This study uses historical earthquake data and virtual earthquake sources to simulate the propagation of seismic waves in urban areas in SW Taiwan. However, due to the limited number of existing free-field seismic stations and insufficient installation density, the accuracy of earthquake damage assessment is directly affected. Past research has pointed out that the use of scenario earthquake simulation can effectively simulate ground motions in local areas. Therefore, the goal of this study is to use numerical methods to construct a 3D seismic wave simulation, using numerical data and virtual seismic observation stations to simulate regional scales. However, due to limitations in computing resources and underground structure information, seismic waves calculated by 3D seismic wave propagation simulations can only cover relatively low-frequency (<1 Hz). However, for structural analysis in urban areas, in addition to inputting this relatively low-frequency signals, it is also necessary to utilize seismic waves covering high frequencies (>1 Hz) to calculate the vibration process and seismic resistance of the structure. Therefore, the goal of this study is to calculate low-frequency and high-frequency seismic waves separately, and to obtain broadband seismic waves containing low-frequency and high-frequency information through a hybrid method. The findings could be applied to future earthquake risk and building damage assessments.

How to cite: Wen, S., Yeh, Y., and Tu, K.-T.: Simulation and Analysis of Disastrous earthquakes in the plains of SW Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14234, https://doi.org/10.5194/egusphere-egu24-14234, 2024.

vX4.14
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EGU24-16216
|
ECS
Eduard Koči and Fridrich Valach

The magnetic storm that occurred in May 1921 ranks among the most extreme events ever observed by magnetic observatories. Some parts of this storm were also recorded in declination and vertical intensity by the variation station at the Stará Ďala observatory (present-day Hurbanovo in Slovakia). However, the magnetogram on photographic paper for this event not only contained data gaps, it also did not have a marked timeline, and the values of the divisions for the geomagnetic elements were not known. We identified timestamps using global variations observed by other observatories and estimated the values of the divisions based on data from before and after the studied event. Then, the magnetograms were digitized. To interpret the obtained data, we compared them with hourly averages from other observatories in different parts of the globe. Our results seem to confirm the expected assumption that, in the morning hours of 15 May 1921, the equatorward boundary of the auroral oval extended to the European mid-latitude observatories.

How to cite: Koči, E. and Valach, F.: The extreme geomagnetic storm on 13–15 May 1921: a study based on hourly means, including observations at Stará Ďala (Hurbanovo), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16216, https://doi.org/10.5194/egusphere-egu24-16216, 2024.