Electric and Magnetic Recordings by Chieti CIEN Station During the Intense 2016–2017 Seismic Swarms in Central Italy

Abstract

We monitored electric and magnetic fields synchronously and continuously in an Italian area prone to moderate-to-high magnitude seismic activity. Identifying and monitoring of potential precursors may contribute to risk mitigation. A decade after the Central Italy Electromagnetic Network started, nine strong shakes with magnitudes between 5.0 and 6.6 occurred in Central Italy between August 2016 and January 2017. The events produced a fault offset of up to 2.8 m along a NNW-SSE normal fault system, 75 km long and located NW of the fault system, which generated the destructive L'Aquila 2009 earthquake sequence. This paper describes the electric and magnetic variations in the extremely low frequency band recorded at the Chieti Station of the network. Meteorological and geomagnetic data were compared to the recordings of these electric and magnetic activities by statistical correlations. We recorded several abrupt increases in electric and magnetic activities not simultaneous to the main seismic events and presumptively related to them. Electrical signals consist in discrete electric field oscillations between 50 and 200 Hz, with time lapses lasting between 3 and 45 min. In addition, magnetic signals consisting of magnetic field pulses with time lapses greater than 10 m were recorded in the same time interval. Similar signals occurred during the 2009 L'Aquila, Central Italy, sequence. Days before each strong earthquake, both electric and magnetic phenomena increased in intensity and number. Two physical models are proposed to describe and interpret electric and magnetic signal events. A number of hypotheses about the origin of recorded electric and magnetic signals may fit coherently with electromagnetic theory and are discussed in the light of a consistent dataset.

Lithosphere–Atmosphere–Ionosphere Coupling Effects Based on Multiparameter Precursor Observations for February–March 2021 Earthquakes (M~7) in the Offshore of Tohoku Area of Japan

“…Furthermore, Schekotov et al ( 2017) [93] found the same ULF/ELF emissions before the recent Kumamoto EQs as well, and it seems that these ULF/ELF emissions are likely generated for any EQs, either inland-fault-type or oceanic-sea-type EQ. Recently, Fidani et al (2020) [81] presented further evidence of these ULF/ELF emissions in the same frequency for the EQs in Europe with the use of their Italian network. Their characteristics, such as impulsive nature, frequency range, and lead time, are very consistent with our statistical summary by Schekotov and Hayakawa (2017) [82] and Hayakawa et al (2019) [83], but unfortunately, they did not provide any statistical study as ours.…”

“…Even though a statistical study on this phenomenon was first published by Schekotov et al (2007) [78], this effect is not so popular either in the academic society. However, recently, Fidani et al (2020) [81] confirmed the presence of this ULF/ELF impulsive radiation with their Italian network and suggested it as a short-term EQ predictor, but unfortunately, they have not yet provided any statistical study as in [78,80,82,83].…”

West Pacific Earthquake Forecasting Using NOAA Electron Bursts With Independent L-Shells and Ground-Based Magnetic Correlations

“…After having stressed that a statistical correlation between two time series does not generally mean that they are physically related (Aldrich, 1995), the hypothesis concerning a physical link between EBs and EQs was studied. A recent observation of magnetic pulses recorded before strong EQs in Central Italy provided recorded magnetic intensities with a diffuse current model (Fidani et al, 2020). This model can push back to the hypocenter region the causal connection of physical events, even if the deduced magnetic inductions in the ionosphere must be demonstrated to be able to modify the electron pitch angles.…”

“…Even if other processes have been proposed more recently, such as the injection of radioactive substances and charged aerosols into the atmosphere, leading to a change in the vertical electric current in the atmosphere and to a modification of the electrical field in the ionosphere (Sorokin et al, 2001), from a solidstate physics perspective (Freund, 2011), and radioactive ionization to model the lithosphere-atmosphere-ionosphere-magnetosphere coupling by the latent heat flux (Pulinets et al, 2015), by AGW (Yang et al, 2019;Piersanti et al, 2020). Recent measurements of magnetic pulses on the occasions of strong EQs (Bleier et al, 2009;Orsini, 2011;Nenovski, 2015) have suggested an efficient process which may influence the ionosphere (Fidani et al, 2020). In this latter work, the magnetic data analysis at the Chieti Station of the Central Italy Electromagnetic Network, performed using two independent sample systems of the same signal, showed that a large number of pulses were recorded in the ELF band below 10 Hz with amplitudes mostly in the range of 2.5-80 nT.…”

“…Relations (Eq. 2) and (C4) of the study by Fidani et al (2020) were used for the wire and the strip, respectively. Moving away from the current density, magnetic inductions generated by the wire and the strip become equal, when the distance overcomes the strip width.…”