Multiple parameters anomalies appeared before medium-strong earthquakes have long been observed and analyzed. The spatio-temporal relations of multiple anomalies were attributed to the coupling of lithosphere, coversphere, atmosphere and ionosphere (LCAI in brief) related with the seismogenious activity and final shocking. However, the mechanism of LCAI coupling is not yet clear and the process of LCAI coupling is much fuzzy, which hinders the scrutinizing of reported anomalies, and leads to great difficulty in discriminating the inconsistency for single parameter as well as the uncertainty among multiple parameters.

From laboratory experiments on rock specimens partly loaded to fracturing we discovered that there were pressure stimulated rock current (PSRC) developing with the applied pressure, and there was stepped increment of PSRC as well as sharp rise of PSRC appearing in the late phase of loading rock to failure. The measured PSRCs were measured in an amplitude of 2~8000na, which depending on rock-minerals and porewater of different rock specimen. The enhancement of surface infrared radiation and the reduction of surface rock dielectric, which lead subsequently to the enhancement of microwave brightness temperature (MBT), could be attributed the production of PSRC and its propagation to rock surface both in laboratory and seismogenious zone.

Ground observations in Luding, China, and Fukushima, Japan, showed that the arriving of PSRC from underground was able to disturb the near-surface electric field, and led further to the local atmospheric ionization and earthquake light near ground surface. Abnormal drop of atmospheric electric field and simultaneous rise of MBT were observed preceding the M6.8 Luding earthquake, 2022, and earthquake lighting and horizontal magnetic vector disturbance were observed accompanying with the M7.3 Fukushima earthquake, 2023.

The arrival of PSRC from seimogenious zone or hypocenter is to change the atmospheric electric field, which was believed being able to penetrate upward from ground surface to ionosphere. An atmospheric electric field penetration model was modified and used to simulated the ionospheric disturbance due to the seismic PSRC inhomogeneous appeared on ground surface. The ionospheric TEC disturbance related with the M8.0 Wenchuan earthquake in 2008, the M9.0 Tohoku earthquake in 2011, the M7.8 Nepal earthquake in 2015 and the M7.5 Turkey earthquake in 2022 were carefully simulated, respectively, according to the position of MBT anomalies or supposed PSRC occurrence. The simulation results were visualized in a 3D spheroid space and contrasted to the reported TEC anomalies retrieved from satellite or ground observations. Particularly for the great Nepal earthquake in 2015, we scrutinized the observed multiple anomalies, including TEC and VLF, possible related with the LCAI coupling, and rooted the seismic anomalies to the simulated underground high-stress accumulation regions on and above the subduction fault.

How to cite: Wu, L., Xie, B., Wu, D., Wang, X., Wang, Z., Ding, Y., Xu, Y., and Mao, W.: Seismic LCAI Coupling Supported by Pressure Stimulated Rock Current: Multi-parameter Observations and Numerical Simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20006, https://doi.org/10.5194/egusphere-egu24-20006, 2024.

Nicaragua is located on the western margin of the Caribbean plate near its interaction with the Cocos plates. The Caribbean plate is surrounded by four major tectonic plates: Cocos at the southwest, Nazca at the south, the North American and South American to the north and southeast respectively. The Cocos plate subducts the Caribbean plate at rates of aproximately 70 to 90 mm/yr having a steeper dip around 75° and 80°. The Central American subduction zone is seismically active. The associated volcanic arc consists mainly of basaltic-andesitic quaternary volcanic rocks (predominantly pyroclastic and lava flows). The seismicity, although constant, has not exceeded earthquakes of Ms 7.3. We analyzed the period between 2000 and 2023 in terms of entropy in natural time domain. Our analysis in terms of Gutemberg-Richter law shows b-value fluctuation ranging between 0.53 and 1.03 by year. Regarding the analysis of entropy fluctuations, it indicates the correlations are short-range, so we consider that the seismic sequence behaves as a Markovian process.

How to cite: Flores-Marquez, E. L., Zambrana-Areas, X. E., and Ramirez-Rojas, A.: Nicaragua seismicity study in terms of entropy fluctuations in natural time domain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12838, https://doi.org/10.5194/egusphere-egu24-12838, 2024.

It is well established in geosciences that M_w > 4 earthquakes are expected to produce changes in the geochemistry of the waters circulating close to epicentral area. Therefore, such modifications are commonly considered as precursory signals and strictly related to the earthquake preparation processes and seismic cycles. Since most of these changes are transitory and site-sensitive, the identification of possible and suitable seismic precursors represents one of the major challenges for geoscientists. Consequently, the development of multi-parametric water monitoring networks located in earthquake-prone areas is a fundamental step toward a better understanding of the relationship between the seismic cycle and the occurrence of possible tracers.

The northern offshore area of the Marche Region was hit by 5.2 and 5.5 M_w earthquakes (Lat. 43.9830, Long. 13.4240, 5 km depth) on November 9, 2022 during which no fatalities or serious damages were recorded. In this work we report the preliminary results obtained from a pre- and post-seismic monitoring focused on waters collected from three piezometers (with a depth ranging from 15 to 30 m) located in the Mt. Conero Area (central-eastern Italy): Monte Acuto (MAC), Vallemiano (VAL), and Betelico (BET), situated ca. 40-50 km from the epicenter. All waters were sampled within 48 hours from the mainshock and periodically (on a monthly or quarterly basis) collected for one year after the event. The water chemistry of BET sample was available from May to October 2022, i.e., up to six months before the event. While the water samples MAC and VAL did not show any relevant chemical and isotopic variations, those collected from BET displayed strikingly significant modifications. The geochemical facies, characterized by a calcium-bicarbonate and a TDS (Total Dissolved Solids) < 1000 mg/L, typical of shallow aquifers, indeed became sodium-chlorine with TDS > 3500 mg/L, since the end of June 2022, i.e., about four months before the mainshock. About a week after the main events, the water chemistry returned to be Ca-HCO₃. Boron, Li, Sr and Rb concentrations also showed significant increments starting from June whereas those of Fe, Mn, Ni, Cu, Zn and Pb displayed overwhelming increases (up to 50 times their pre-seismic values) in those samples collected in the days following the mainshocks. Consequently, particular emphasis was placed on addressing the origin of these changes and evaluating their possible relation with the seismic event. We can hypothesize that a mixing process between shallow aquifer and Na-Cl connate (or thermal) waters occurred, the latter being widely reported in the Adriatic foredeep deposits. The observed chemical variations might likely be related to changes in the relative pressure between superimposed and separated aquifers triggered by modifications in the stress rates associated with the seismic cycle. Moreover, variations in the hydraulic heads resulting in a temporary connection between two distinct aquifers would also explain the transitory changes detected at BET. If confirmed, these variations would be among the most strikingly impressive geochemical evidences ever detected before a seismic event or, at least, ever reported in the literature.

How to cite: Chemeri, L., Taussi, M., Fronzi, D., Cabassi, J., Tazioli, A., Renzulli, A., and Vaselli, O.: Groundwater geochemical anomalies in Mt. Conero area (central-eastern Italy) related to the pre- and post- 5.2 and 5.5 Mw Marche offshore seismic events (November 9, 2022), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7299, https://doi.org/10.5194/egusphere-egu24-7299, 2024.

This work presents some results achieved in the frame of TILDE project (Tidal Interplate Lithospheric Deformation of Earth). The main goal of TILDE project was the estimation of Local Solid Earth Tides (LSET); i.e. models which depends on the geographical position of the selected sites. The LSET models are built estimating Love and Shida numbers for each station and for each tidal constituents. The objectives were to investigate possible correlations between LSET and geological/geophysical events, such as tectonic plates movements, earthquakes and volcanic activities. GNSS data collected at 98 stations, split into global and regional networks have been used. The global network consists of 73 GNSS stations which have piled up a stack of data 20 years long. The regional networks consist of 25 stations, 7 located in New Zealand, 1 in Kamchatka, and 17 stations in Italy for which 3 year-long time series of data are available.

The LSET models have been achieved using GNSS coordinates expressed both in geocentric XYZ and local NEU references, estimated in Precise Post Processing mode, with a sampling rate in turn of 1 day and 3 hours.  Different GNSS solutions have been generated according the objectives of the project. The first one is the background solution in which the full IERS2010 tides model has been applied. The second solution is obtained by switching off the tides model. The third one is the solution in which only the Long-Periodic Tides (LPT) has been switched off. This last solution has been applied in order to lower the level of flickering of GNSS time series when Love and Shida numbers of LPT had to be estimated.

This analysis showed that there is a correlation between the latitude measured from the tectonic equator and Love numbers. This confirms the theory that moon tides contribute to trigger tectonic movements.

An interesting result, relevant for the assessment and potential precursiveness of the risk of seismic hazards, was the correlation found between the variation in time of Love numbers of diurnal (K1) and semi-diurnal (M2) tides and the occurrence of earthquakes nearby GNSS sites.  At this purpose we selected GNSS global stations which were at a distance <200 Km from the epicentre of EQ events. The investigation has outlined that almost the seismic events are got ahead by a downfall of Love numbers. It seems that each earthquake event cannot be characterized only by the type of slip occurred along faults: compressive (i.e., reverse fault), extensional (i.e., normal fault), strike slip or combination of them. This result could be explained with the rigidity of the crust/mantle which play a major role in triggering seismic events. For smaller values of Love number we have indeed a more rigid response of Earth to Tidal forcing.

How to cite: Vespe, F., Dousa, J., Doglioni, C., Ficini, E., Masci, O., Nico, G., Nosek, J., Vaclavovic, P., Sottili, G., Zaccagnino, D., Mendes, L., and Amarillo-Fernandez, F.: Local Solid Earth Tides and Their potential use in assessing and forecasting the risk of seismic hazards, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13120, https://doi.org/10.5194/egusphere-egu24-13120, 2024.

How to cite: Shen, X., zhang, X., Zeren, Z., Zhao, S., Liu, Q., Battiston, R., De Santis, A., Liu, T., Tramutoli, V., Conti, L., and Yan, R.: 6 years results of EQ precursors research by using CSES-01 onboard and the following step of  IMCP , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3264, https://doi.org/10.5194/egusphere-egu24-3264, 2024.

We investigate the recent earthquakes (EQs) that occurred on 06 February 2023 principally in the central southern part of Turkey and north western of Syria. The tectonic plate movements between Anatolian, Arabian and African plates are well known to be subject to EQs. The coordinate of the epicenter was 37.08°E and 37.17°N with depth in the order of 10 km and a magnitude Mw7.8. Beside aftershocks, a few hours later a strong Mw7.7 earthquake occurred in the same region . We consider in this analysis the Bafa VLF transmitter (TBB) signal emitting at frequency of 26.7 kHz and localized in the Anatolia region (Turkey) at longitude of 27.31°E and latitude of 37.40°N. TBB transmitter signal is daily monitored by the VLF Graz facility (Biagi et al., 2019; Galopeau et al., 2023) with a sufficient signal to noise ratio principally during night observations. We study the variations of the phase and amplitude of TBB signals, as detected by Graz facility (15.43°E, 47.06°N) few weeks before the earthquakes occurrence. It is essential to note that the geographical latitudes of the epicenter and the TBB transmitter are about 37°N, and the distance, in the order of 850 km, is found smaller than the radius of the earthquake preparation zone, as derived from Dobrovolsky et al. (1979), when considering the magnitude of the seismic event, i.e. Mw7.8. We have applied the terminator time (TT) method to make evident the presence of sunrise and sunset time shifts at terminators one week to ten days before EQs.  We discuss essentially the anomalies, in the phase and the amplitude of TBB transmitter, which are probably linked to the electron density variations at the formation and the destruction of the ionospheric D-E-layers.

References:

Biagi et al., The INFREP Network: Present Situation and Recent Results, Open J. Earth. Research, 8, 2019.

Dobrovolsky et al., Estimation of the size of earthquake preparation zones, Pageoph, 117, 1979.

Galopeau et al., A VLF/LF facility network for preseismic electromagnetic investigations, Geosci. Instrum. Method. Data Syst., 12, 2023.

How to cite: Boudjada, M. Y., Biagi, P. F., Eichelberger, H. U., Galopeau, P. H. M., Schwingenschuh, K., Solovieva, M., Nico, G., Lammer, H., Voller, W., and Stachel, M.: Study of VLF phase and amplitude variations before the Turkey Syria Mw 7.8 EQs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10341, https://doi.org/10.5194/egusphere-egu24-10341, 2024.

The Fracture-Induced Electromagnetic Radiation (FEMR) phenomenon has been substantially investigated as a prolific geophysical tool and provided a precursor to geohazards such as landslides, earthquakes, and rockburst hazards. Several lab-scale experiments on materials such as chalk, rocks, glass, ceramics, granite, etc., have been conducted to correlate between experimental observations and theoretical formulations of the physical parameters of FEMR generations such as crack dimensions, crack velocity, frequency of crack propagation, and finally draw an analogy with earthquake events. The FEMR working principle for Earth’s fracture detection is based on generating geogenic electromagnetic radiation from the brittle rock bodies subjected to differential stress in the near-surface of the Earth’s crust. When external stimuli, such as significant deviatoric stresses in thrust or shear zones due to active tectonic forces, induce stress on these rock bodies, microcracks form and propagate. The "Process zone" at the crack tip contains numerous microcracks and dipoles that emit FEMR waves in the kHz to MHz frequency range. As microcracks coalesce and lead to macro failure, the amplitude of FEMR pulses diminishes. FEMR pulses show less attenuation than seismic waves, making them a more efficient precursor to potential tectonic activities. They are an early warning sign for earthquakes a few hours or days before the event. The current study consisted of FEMR surveys along a segment of the active Dead Sea transform (DST) from Sodom to Jericho. This coincided with a 6.3 magnitude (M_w) aftershock earthquake (EQ) in the Turkey-Syrian region on February 20, 2023, where the last measurement was taken 2 hours before the EQ. Several FEMR parameters (e.g., Benioff strain release, frequency, rise time, hits or activity, and energy) along with their associated crack dimensions were analyzed after filtering the raw data and comprehending their trends leading up to the EQ. This study investigated the Benioff Strain plot and other parameters in three consecutive stages of earthquake nucleation leading to the EQ. In the first stage, there's an increase in FEMR hits and frequency, accompanied by a decrease in rise time (T') and crack dimensions. The second stage is characterized by a decline in FEMR hits and crack width while all continue to increase. Notably, the second stage accumulates the second highest energy, likely due to a high-stress drop. The third stage features a steady increase in FEMR hits and energy and an abnormal increase in crack dimensions, perhaps signifying an upcoming event of macro failure. The cyclic trend in FEMR hits suggests periods of high activity and silence, possibly related to stress changes during crack propagation. Because the measurements were taken a few hours before the earthquake, this survey provides valuable insights into the modulation of FEMR parameters before an earthquake. The results obtained from this analysis could bridge the gap between lab-scale and large-scale studies of stress-induced rock collapses and provide a befitting precursor to such disastrous natural calamities.

How to cite: Das, S. and Frid, V.: The Fracture Induced Electromagnetic Radiation (FEMR) induced along the Dead Sea Transform fault before the Syrian-Turkey earthquake (Mw-6.3) on 20.2.2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-360, https://doi.org/10.5194/egusphere-egu24-360, 2024.

We study critical lithosphere/atmosphere /ionosphere coupling processes that precede earthquake events. Soon after the M7.8 and M7.5 in Kahramanmaraş, Türkiye on Feb 6, 2023, Kahramanmaraş earthquakes, we started collecting and processing multi-parameter data from ground, atmosphere, and satellite observations, such as 1/ Vertical static pendulums data from the European network; 2/ Hydrogeochemical data for electrical conductivity and major ion contents from the spring water samples near Kahramanmaraş ; 3/ Outgoing long-wavelength radiation (OLR) obtained from satellites NPOESS; 4/ Ionospheric plasma observations from China/Italy Seismo-Electromagnetic Satellite (CSES1);5/Electron density variations in the ionosphere via GPS Total Electron Content (GPS/TEC) and 6/ Atmospheric chemical potential (ACP) obtained from NASA assimilation models. We have detected two temporal groups of pre-earthquake anomalies: A/few months in advance - hydrogeochemical anomalies lasting up to six months and vertical static pendulums lasting two months ahead of the seismic rupture and B/few days in advance -  OLR and ACP anomalies showed an abnormal increase on Jan 15-30, along with the plasma electron and oxygen ion density from the CSES1 satellite which is highly correlated with electron density variations in the ionosphere from GPS/TEC. Two groups of identified anomalies relate to different stages of Kahramanmaraş earthquake preparation processes. The first type was linked to the crustal deformation phase and was associated primarily with the coupling processes of the lithosphere-atmosphere. Based on the cross-event analysis of major seismicity in the regions, we found similarities in the pre-earthquake pattern occurrence between the M7.8/M7.5 2023 Kahramanmaraş sequence and the M7.2 Van Earthquake of 2011 and two other major events.

We show that we could extract new information about the different stages of earthquake preparation processes by combining ground and near-space data according to the physical concept of LAIC.

How to cite: Ouzounov, D., Inan, S., Kalenda, P., Neumann, L., Pulinets, S., Liu, J.-Y., Shen, X., Yan, R., Rušajová, J., Kafatos, M. C., and Taylor, P.:  Multi-parameter study of the pre-earthquake phase associated with the Kahramanmaraş sequence in Türkiye on February 6th, 2023. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6407, https://doi.org/10.5194/egusphere-egu24-6407, 2024.