Ionospheric Effects of Natural Hazards in Geophysics: From Single Examples to Statistical Studies Applied to M5.5+ Earthquakes

Abstract

Geophysical natural hazards, such as earthquakes and volcano eruptions, can have catastrophic effects on the population depending on the location and quality of construction. From the geophysical point of view, several aspects are still debated in the preparation phase of such events. In particular, several theories proposed that prior to the earthquake and volcano eruption, the releases of gas, fluids or charged particle from the lithosphere (e.g., the fault for the earthquake) could create some effects on the atmosphere and ionosphere. In this work, several single examples will be shown of possible candidates of pre-earthquake ionospheric disturbances recorded by the China National Space Administration (in partnership with the Italian Space Agency) China Seismo Electromagnetic Satellite (CSES) or European Space Agency Swarm constellation. The examples will show anomalous ionospheric status in terms of magnetic disturbances or increase of electron density before earthquakes like Mw = 7.1 Ridgecrest (US) 2019 or during the large recent volcano eruption of Hunga Tonga-Hunga Ha'Apai of last 15 January 2022. In these cases, some couplings between the lithosphere and ionosphere are proposed. Finally, verifying if such ionospheric disturbances proceeded for "chance" or are really linked to the incoming event is a crucial point. For this purpose, we performed worldwide statistical studies, not only supporting the recurrence of such phenomena for about 15% of M5.5+ shallow earthquakes but also showing a link between the magnitude of the upcoming seismic events and the pre-earthquake anticipation time. Furthermore, we also show the influence of the location (sea or land) on the frequency of the ionospheric electromagnetic disturbance.

Study on Electron Density Anomalies Possibly Related to Earthquakes Based on CSES Observations

“…Finally, it seems that from about 2 weeks before the earthquake up to its occurrence, the number of recorded anomalies increased. This suggests that the incoming earthquakes induced some ionospheric disturbances, which in agreement with previous statistical preliminary investigations made on CSES Ne that reported more anomalies before the seismic events than after [27].…”

Atmospheric and Ionospheric Effects of La Palma Volcano 2021 Eruption

“…For the extension of the area, we take into account that firstly, the satellites are flying at an altitude of about 500 km, so a smaller diameter would not be reasonable, as stated in [67]. We also need to consider that the plume has been transported by the wind during this period, and we may expect a possible coupling with the atmosphere both straight with the volcano activity (so above La Palma Island) or at above the plume as possible coupling with the volcano activity may be indirect as in the case of Hunga Tonga Hunga Ha'Apai that was reported a possible LAIC in ionosphere with the pressure wave produced by the extreme explosion [68,69]. A radius of 380 km was finally selected.…”

CSES-01 Electron Density Background Characterisation and Preliminary Investigation of Possible Ne Increase before Global Seismicity

“…Previous investigations of possible seismo-ionospheric anomalies in a single case study include among them the Mw = 6.2 L'Aquila (Italy) 2009 earthquake by Piersanti et al [22], Mw = 6.7 Lushan (China) 2013 by Zhang et al [23], Mw = 7.8 Nepal 2015 earthquake by De Santis et al [24], Ghamry et al [25], Fan et al [26], Ouzounov et al [27] and Wu et al [28], Mw = 6.5 Amatrice-Norcia (Italy) 2016 seismic sequence by Marchetti et al [29,30], Mw = 7.5 Indonesia 2018 earthquake by Marchetti et al [31], Mw = 7.6 Papua New Guinea 2019 earthquake by Akhoondzadeh et al [32], Mw = 7.1 earthquake by De Santis et al [33] and Marchetti et al [34,35], Mw = 7.2 Kermadek Islands 2019 earthquake by De Santis et al [36], and the recent Mw = 7.8 Turkey 2023 earthquake [37]. A recent investigation by Marchetti et al [38] of the Mw = 3.3 Guidonia (Rome, Italy) small earthquake that occurred on 1 January 2023 does not identify any possible seismo-induced effect, confirming that a lower magnitude event was unlikely to have caused perturbations in the ionosphere, but on the other side it proposed that some Swarm ionospheric disturbances could be related to the Mw = 5.5 event that occurred in November 2022 in the Adriatic sea.…”

“…Statistical studies dedicated to electron density from DEMETER have been performed by Yan et al [46], identifying a statistically significant increase in anomalies about 5-6 days before M5+ earthquakes. De Santis et al [47] and Marchetti et al [34] correlated electron density variations measured by CSES LAP with M5.5+ shallow (depth ≤ 50 km) earthquakes. They identified an increase in anomalies 20 days before the earthquakes and that the anomalies in the three months before earthquakes are more numerous than the ones recorded in the three months after the earthquakes, suggesting that the difference may underline the LAIC effects of the preparation of the investigated earthquakes.…”

“…Considering that here we are not comparing the absolute value of electron density with other satellites or measurements and that CSES-01 LAP data are auto-consistent, we consider the discussion on the absolute value to be beyond the scope of the present paper as not influencing the conclusions of the presented analyses. The observations of CSES-01 not only provide important results for a better understanding of earthquakes, but they permit to investigate and comprehend other geophysical phenomena such as geomagnetic storms [64,65], volcano eruptions (for example, the La Palma 2021 eruption [66] and the extreme explosion on 15 January 2022 of the Hunga Tonga-Hunga Ha'Apai volcano [34,67]), or magnetic pulsations Pi2 [68]. The magnetic data of the CSES also contributed to the 13 • generation of the IGRF geomagnetic model [69] and provided an independent model for equatorial regions [70].…”