An instrumental array was established in southwest China for Monitoring Vibrations and Perturbations in the Lithosphere, Atmosphere and Ionosphere (MVP-LAI).  We retrieved multiple-geophysical data from the array to investigate common characteristics in LAI before earthquakes.  Broadband seismometers are utilized to monitor ground vibrations in the lithosphere.  Barometers record changes in air pressure near the Earth’s surface.  Magnetometers monitor variations in the ionospheric currents ~100 km above the Earth’s surface.  Instead of GPSTEC (Global Positioning System Total Electron Content), electromagnetic signals transmitted from the BDS (BeiDou navigation system) geostationary satellites are received by ground-based GNSS (Global Navigation Satellite System) receivers to compute TEC data.  The BDSTEC from the geostationary satellites continuously monitor changes in TECs ~350 km in altitude right over the array.  We transferred these data into the frequency domain and found that ground vibrations, air pressure, the magnetic field, and BDSTEC data share the frequency ~5×10^-3 Hz before major earthquakes.  Ground vibrations exhibit frequency characteristics of ~5×10^-3 Hz due to resonance of nature frequencies before failure of materials (i.e., dislocations of faults, and earthquakes).  Ground vibrations with frequency of ~5×10^-3 Hz persistently hit the bottom of the atmosphere that can trigger atmospheric resonance before earthquakes.  Double resonance (i.e., crustal and atmospheric resonance) provides the new way to reveal the seismo-anomalies of multiple geophysical parameters in LAI.  Double resonance would shed a light in earthquake prediction in practice once we face the major issue for efficiently retrieving resonance signals from multiple observation data. 

How to cite: Chen, C.-H., Lin, K., Zhang, X., and Gao, Y.: Double resonance before earthquakes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2087, https://doi.org/10.5194/egusphere-egu23-2087, 2023.

We present a study on temporal and spatial characteristics of Thermal Radiation anomalies (TRA) and ionospheric total electron content (TEC) pre-earthquake abnormalities associated with the occurred in 2022 “anniversary” earthquakes. “Anniversary”  is a quake occurring on the same date and following the years after the main earthquake, plus or minus several days.

We studied eleven large earthquakes in four regions: i/Japan: M7.3 of 03.16.2022 and M9.0 of 03.11.2011 East Coast Honshu; ii/Mexico: M7.6 of 09.19.2022 Michoacan; M7.1 of 09.19.2017 Puebla and M8.0 of 09.19.1985 Mexico City;/iii Chile: M5.7 02.28.2022 Bio-Bio and M8.8 02.27.2010 Maule and /iv Taiwan: M6.9 of 09.18.2022 Taitung and M7.7 of 09.21.1999 Chi-Chil and M6.7 of 03.22.2022 Taitung and M6 of 03.27.2013 Nantou earthquake.

We analyzed for TRA and TEC anomalies concerning the earthquake preparation zone (EPZ). For EPZ estimates, we use Dobrovolsky et al. (1979), and Bowman et al. (1998) estimates where the EPZ radius scales exponentially with earthquake magnitude, especially from Mw ≥ 6.0 onwards, and gives an extended coverage at larger magnitudes to examine TRA and ionospheric TEC anomalies. The main goals of this study were: 1/to understand the seismotectonic conditions that preceded the earthquake re-occurrence in the same place and on the same day(s): 2/ to perform a validation study about pre-earthquake signal occurrences in the same atmospheric and solar-geophysical conditions and 3/ to understand the potential triggering mechanism. Our preliminary results show synergetic coordination between the appearance of pre-earthquake transients’ effects in the atmosphere and ionosphere (with a short time lag, from hours up to a few days). The spatial characteristics of pre-earthquake anomalies were associated with the large area but inside the preparation region estimated by Dobrovolsky-Bowman. The pre-earthquake nature of the signals in the atmosphere and ionosphere was revealed by simultaneous analysis of satellite, GPS/TEC, and Satellite Earth observations. The “anniversary” events are recognized with common pre-earthquake transient re-occurrence patterns in the atmosphere/ionosphere within EPZ, scaled to the extent of the earthquake magnitude.

How to cite: Ouzounov, D., Pulients, S., Liu, J.-Y., Hattori, K., Kafatos, M., and Taylor, P.: Transient effects in the atmosphere/ionosphere and their re-occurrence before large earthquakes. Case study for the 2022 “anniversary” events., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4399, https://doi.org/10.5194/egusphere-egu23-4399, 2023.

WATER’S GEOCHEMICAL COMPOSITION AS INDICATOR OF GEODYNAMIC ACTIVITY 

A.Kazarian, H. Kazarian IGN AN NAN

A detailed analysis of a long-term collection of hydro-geochemical data was carried out over a ten-year period. It revealed consistent iterations of signs of a process of earthquake preparation in this region. This preparation process has several distinct stages, which can be identified by noticeable changes in the geochemical composition of self-pouring well water. The earthquake preparation process is graphically visible and has a similar duration to the post-earthquake aftershock activity duration. The visualization of hydro-geochemical data from the pre- and post-earthquake periods for different (M> 6) earthquakes in this region shows a very similar pattern of behaviors and duration of behaviors for events of varying magnitudes and distances from the observation wells.

Changes in the main fluctuation trend of the geochemical data for helium (He) and a decrease in the standard deviation of the series for other main components appear as earthquake precursors (Na, K, HCO3, SO4, Cl, Ca, F). The detectable duration of a main shock's preparation process is approximately a year. The detailed examination of the data time series reveals a strong correlation between the overall geodynamic activity of the region and the hydrogeochemical composition of the observed wells.

The detailed analysis of earthquake activity in the region suggests a periodic nature of basic seismicity and its relationship with earthquake focal mechanisms. The obtained daily histograms for seismic activity in Armenia, Turkey, Greece, and Italy regions calculated by local time show cyclical activity patterns of 24 and 12 hours. This is consistent with variations in He and other important components in the well waters. The hypothesis and conclusion of this scientific research project are that in seismically active zones, the dynamics of hidden active tectonic processes can potentially be a priori diagnosed using this hydro-geochemical monitoring method.

How to cite: Kazarian, A. and Kazarian, A.: Water chemical composition as indicator of geodynamic activity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3596, https://doi.org/10.5194/egusphere-egu23-3596, 2023.

The North-South Seismic Belt of China is one of the most active seismic areas on the Chinese continent.  More than ten strong earthquakes (Ms > 6) have occurred in this region since 2010.  However, Earthquake-related conductivity anomalies are rarely reported for those earthquakes.  In this study, 3-component geomagnetic data recorded at sixty geomagnetic stations are selected to compute the Parkinson vectors to monitor the changes of conductivity before and after the earthquakes.  Considering most fluxgate magnetometers have only been installed since 2014, we concentrate on six Ms > 6 earthquakes occurred during 2014–2019.  To mitigate artificial disturbances, low noise data during the 00:00 – 5:00 LT are utilized.  We compute the background distribution and monitoring distribution using the azimuth of the Parkinson vectors at each station within six years (2014 – 2019) and a 15-day moving window, respectively.  The background distribution is subtracted from the monitoring distributions to mitigate the influences of underlying inhomogeneous tectonic structures.  The obtained difference distributions binned by 10° within 400 km from each station are superimposed during 60 days before and after the earthquake to construct integrated maps.  To analyze the potential frequency characteristics, we compute the results from low to high frequency band.  The results show that for four earthquakes, the conductivity anomalies areas appear near the epicenter 10 to 20 days before earthquakes, while the rest two earthquakes have no anomaly.  The conductivity anomalies appear at all study frequency band from 0.0005 Hz to 0.1 Hz, and significantly at 0.001 – 0.005 Hz before earthquakes.  Meanwhile, we find that the lower frequency band corresponds to larger anomalies area.  These results suggest the change of underlying conductivity near the hypocenter is a possible phenomenon for strong earthquakes, and the frequency characteristics of the seismo-conductivity anomaly during the earthquake are helpful to understand the pre-earthquake anomalous phenomena.

How to cite: Mao, Z. and Chen, C.-H.: Conductivity Anomalies before M > 6 Earthquakes in China during 2014 – 2019, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10627, https://doi.org/10.5194/egusphere-egu23-10627, 2023.

The mission of Advanced Ionospheric Probe (AIP) onboard FORMOSAT-5 (F5) satellite is to detect seismo-ionospheric precursors (SIPs) and observe ionospheric weathers.  F5/AIP plasma quantities in nighttime of 22:30 LT (local time) and the total electron content (TEC) of the global ionosphere map (GIM) are used to study SIPs of an M7.3 earthquake in the Iran-Iraq Border area on 12 November as well as two positive storms on 7 and 21-22 November 2017.  The TEC and the F5/AIP ion density/temperature anomalously increase over the epicenter area on 3-4 November (day 9-8 before the earthquake) and on the two storm days.  The anomalous TEC increase frequently appearing specifically in a small area near the epicenter day 9-8 before the earthquake indicates the SIP being observed, while those frequently occurring at worldwide high-latitudes are signatures of the two positive storms.  TEC increase anomalies most frequently appearing in the Iran-Iraq Border area on 21-22 November (day 10-9 before) is coincidently followed by an M6.1 earthquake on 1 December 2017, which again meets the temporal SIP characteristic.  The F5/AIP ion velocity uncovers that the SIPs of the two earthquakes are caused by eastward seismo-generated electric fields, and the two positive storms are due to the prompt penetration electric fields.

How to cite: Liu, J.-Y., Chang, F.-Y., Chen, Y.-I., and Chao, C.-K.: Ionospheric electric fields associated with seismo-ionospheric precursors and ionospheric storms observed by FORMOSAT-5/AIP, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17023, https://doi.org/10.5194/egusphere-egu23-17023, 2023.

We report on two earthquakes (EQs) that occurred in Croatia at a distance less than 200 km from the Austrian Graz facility (15.46°E, 47.03°N). Those EQs happened on March 22 and December 29, 2020, with magnitudes of Mw5.4 and Mw6.4, respectively. The epicenters were at geographical coordinates (16.02°E, 45.87°N; 16.21°E, 45.42°N) with focuses smaller than 10 km.  Austrian Graz facility leads to detect more than fifteen VLF and LF transmitter signals (Schwingenschuh et al., 2011, Biagi et al., 2019). Transmitter ray paths cross over the EQs epicenters in particular those localised in ICV and ITS (Italy) and TBB (Turkey). We emphasize in our study on the signal fluctuations before/after the sunrise- and sunset-times, or terminator times (TTs). Transmitter amplitude signals exhibit precursor anomalies that related to EQs disturbances occurring particularly at the falling off or the growth of the ionospheric D-layer. Ground-based stations (e.g. Rozhnoi et al., 2009) and satellite observations (e.g. Zhang et al., 2020) have reported such EQs ionospheric disturbances at several occasions.

References:

Biagi et al., The INFREP Network: Present Situation and Recent Results, Open J. Earth. Research, 8, 2019. Rozhnoi et al., Anomalies in VLF radio signals prior the Abruzzo earthquake (M=6.3) on 6 April, 2009, Natural Hazards and Earth System Science, 9, 2009. Schwingenschuh et al., The Graz seismo-electromagnetic VLF facility, Nat. Hazards Earth Syst. Sci., 11, 2011. Zhang et al., Multi-experiment observations of ionospheric disturbances as precursory effects of the Indonesian Ms6.9 earthquake on August 05 2018, Remote Sens. J., 12, 2020.

How to cite: Boudjada, M. Y., Biagi, P. F., Eichelberger, H. U., Schwingenschuh, K., Galopeau, P. H. M., Hayakawa, M., Solovieva, M., Lammer, H., Voller, W., and Besser, B.: VLF transmitter signal variations as detected by Graz facility prior to Croatian earthquakes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9395, https://doi.org/10.5194/egusphere-egu23-9395, 2023.

The temporal sequences of magnitudes recorded in seismic active zones exhibit complex behavior which is associated with the wide diversity of scales of fractures sizes when an earthquake on the Earth’s crust occurs. Earthquakes can be considered to be nearly, or even critical phenomena exhibiting dynamic phase transitions, where a mainshock is the beginning of a new phase. Near the critical point is where phase transition (order-disorder) occurs, and scaling laws with long-range order correlations are produced, so that the complexity of seismicity allows earthquakes to be characterized by a more diverse and riche phenomenology. In the last years, the ideas linked to nonlinear time series analysis and complex network theory have been related. Among those ideas,  the visibility graph (VG) method has been applied to the study different complex phenomena. One of the characteristics of this method is its ability to capture dynamic properties, such as non-trivial correlations in nonstationary time series, without introducing elaborate algorithms such as detrending. Seismic processes have been of great interest and their complete understanding is still an open problem. In this work we use the VG method to study the temporal correlations in the seismic sequences monitored in three regions of the subduction zone belonging to the Cocos plate. Our analysis allows estimate persistence and the temporal correlations in the seismic activity monitored in Michoacan State, Mexican Flat Slab and Tehuantepec Isthmus, showing differences in all three.

How to cite: Ramírez-Rojas, A. and Flores-Márquez, E. L.: Correlations of the seismic activity monitored in three subduction zones belonging to Cocos plate by using the visibility graph method., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10458, https://doi.org/10.5194/egusphere-egu23-10458, 2023.

We have used 2014–2017 data from the eight receiving stations of the Japan very low frequency (VLF) monitoring network. The nighttime data of the signals of the JJI transmitter on Kyushu Island, excited VLF electromagnetic waves (EMWs) in the Earth-Ionosphere waveguide (EIWG) had been processed. The wavelet transform with a preliminary detrending, to exclude influence of daily variations, has been applied. We have observed ultra-low frequency (ULF) modulation of VLF EMW spectra in the EIWG. We therefore concluded that modulating oscillations with periods of 4 minutes belong to the acoustic branch of acoustic-gravity waves (AGWs) in the Earth–Thermosphere waveguide; modulation of VLF with periods of 6–7 minutes corresponds to global evanescent/reactive Brunt–Väisälä AGW oscillations; the oscillations with periods 20–60 min and ~3 hours may characterize evanescent/reactive Lamb gravity wave mode of AGW [1]. The appearance of the combination frequency of VLF EMW and ULF AGW is likely due to the following effects: (1) the drag of charged plasma particles by ULF AGWs jointly with the background of VLF electron density disturbances and (2) the motion of charged plasma particles in the VLF EMW field jointly with the background of ULF changes in the plasma concentration caused by AGWs.

The theory [2,3] is extended to the excitation of ionospheric Schumann resonator (SR) [4] and ionospheric Alfvén resonator (IAR) in the ULF range. It is shown that IAR oscillations with a high quality factor (for geophysical resonators) (>10) can be excited in the SR range. The features of the excited ULF and VLF modes associated with the modification of the ionosphere as a result of the powerful eruption of the Hunga-Tonga volcano are under consideration [5,6].

A ULF model of perturbations in the atmosphere-ionosphere with a boundary transition from dynamic to static limit is developed and the preliminary results of the corresponding modelling will be presented. This ensures the "recovery" of magnetostatic disturbances "lost" in most of previous models of the atmospheric electrical circuit, important for understanding the mechanisms of seismo-ionospheric coupling, volcano-ionospheric coupling and influences of the other natural hazards on the ionosphere and ionospheric monitoring of the natural hazards.

[1] Rapoport et al. Sensors 22, 10.3390/s22218191, 2022; [2] Grimalsky et al. JEMAA 2012, 4, 192-198 ; [3] Yutsis V. et al. Atmosphere 2021, 12, 801 ; [4] Nickolaenko and Rabinovich Space Res. 1982, XX, 67-88 ; [5] Astafyeva et al. GRL, 2022 ; [6] D’Arcangelo et al., Rem. Sens., 14, 3649, 2022.

This research was partially funded by the National Science Centre, Poland, grant No. 970 2022/01/3/ST10/00072

How to cite: Rapoport, Y., Reshetnyk, V., Grytsai, A., Liashchuk, A., Hayakawa, M., Grimalsky, V., Petrishchevskii, S., Krankowski, A., Błaszkiewicz, L., Flisek, P., De Santis, A., and Scotto, C.: ULF perturbations: modeling Earth-Atmosphere-Ionosphere coupling, signal processing using information entropy, determination of the electric and magnetic field components and “experiment-theory comparison“, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13172, https://doi.org/10.5194/egusphere-egu23-13172, 2023.