- 1Space Research Institute, Austrian Academy of Sciences, Graz, Austria (hue@oeaw.ac.at)
- 2Institute of Physics Belgrade, University of Belgrade, Belgrade, Serbia
- 3Schmidt Institute of Physics of the Earth, RAS, Moscow, Russia
- 4Department of Physics, University of Bari, Bari, Italy
- 5LATMOS-CNRS, UVSQ Université Paris-Saclay, Guyancourt, France
- 6Institute for Physics, University of Graz, Graz, Austria
- 7National Institute for Earth Physics, Magurele, Romania
- 8Institute of Applied Mathematics, Italian National Research Council, Bari, Italy
Electric field amplitude and phase measurements between narrowband VLF/LF transmitters and receivers in the sub-ionospheric waveguide are affected and altered by man-made and natural sources (Nina 2024; Boudjada et al., 2024a,b). In this study we investigate Mw≥5.0 earthquakes (EQs) which occurred in Europe during the year 2024 based on data from the INFREP receiver network (Biagi et al., 2019; Moldovan et al., 2015; Galopeau et al., 2023). In the selected Mediterranean area with geographical longitude [-10°E, 40°E] and latitude [30°N, 50°N] the United States Geological Survey EQ catalog (USGS, 2025) provides 20 events with Mw≥5.0. For these EQs we apply the night-time amplitude method and consider variations in the terminator times (Hayakawa et al., 2010). The main radio links that cross the EQ prone areas are from transmitters localized in the southern part of Europe, including TBB (26.70 kHz, Bafa, Turkey), ITS (45.90 kHz, Niscemi, Sicily, Italy), and ICV (20.27 kHz, Tavolara, Italy).
We find statistically significant electric field anomalies for various VLF/LF paths, particularly for events with higher magnitudes. The continuous VLF/LF electric field amplitude and phase datasets can be important parameters for real-time observations and services to assess seismic hazards and disturbing physical phenomena within the waveguide.
References:
Biagi, P.F., et al., The INFREP network: Present situation and recent results, OJER, 8, 101-115, 2019. https://doi.org/10.4236/ojer.2019.82007
Boudjada, M.Y., et al., Unusual sunrise and sunset terminator variations in the behavior of sub-ionospheric VLF phase and amplitude signals prior to the Mw7.8 Turkey Syria earthquake of 6 February 2023, Remote Sens., 16, 4448, 2024. https://doi.org/10.3390/rs16234448
Boudjada, M.Y., et al., Analysis of pre-seismic ionospheric disturbances prior to 2020 Croatian earthquakes, Remote Sens., 16, 529, 2024. https://doi.org/10.3390/rs16030529
Galopeau, P.H.M., et al., A VLF/LF facility network for preseismic electromagnetic investigations, Geosci. Instrum. Method. Data Syst., 12, 231–237, 2023. https://doi.org/10.5194/gi-12-231-2023
Hayakawa, M., et al., A statistical study on the correlation between lower ionospheric perturbations as seen by subionospheric VLF/LF propagation and earthquakes, JGR Space Physics, 115(A9), 09305, 2010. https://doi.org/10.1029/2009JA015143
Moldovan, I.A., et al., The development of the Romanian VLF/LF monitoring system as part of the International Network for Frontier Research on Earthquake Precursors (INFREP), Romanian Journal of Physics, 60 (7-8), 1203-1217, 2015. Bibcode: 2015RoJPh..60.1203M https://rjp.nipne.ro/2015_60_7-8/RomJPhys.60.p1203.pdf
Nina, A., VLF signal noise reduction during intense seismic activity: First study of wave excitations and attenuations in the VLF signal amplitude, Remote Sens., 16, 1330, 2024. https://doi.org/10.3390/rs16081330
USGS, United States Geological Survey earthquake catalog, https://www.usgs.gov/programs/earthquake-hazards, as of Jan 2025.
How to cite: Eichelberger, H. U., Boudjada, M. Y., Nina, A., Besser, B. P., Wolbang, D., Solovieva, M., Biagi, P. F., Galopeau, P. H. M., Schirninger, C., Moldovan, I.-A., Nico, G., Stachel, M., Aydogar, Ö., Muck, C., Wilfinger, J., and Jernej, I.: Sub-ionospheric VLF/LF waveguide electric field investigation from Mw≥5.0 earthquake events with multiple receivers in Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13142, https://doi.org/10.5194/egusphere-egu25-13142, 2025.
