A study to investigate the relationship between ionospheric disturbance and seismic activity based on Swarm satellite data

Abstract

The 7 years electron density data observed by the Swarm constellation and 527 earthquakes with M ≥ 6.0 are used to investigate the relationship between ionospheric disturbances and seismic events. The disturbances of the ionospheric electron density, defined as the difference between the orbital observation data and its fitting data, are considered to be possible signals of the seismic activity and are often reported before or after earthquakes near the epicenter. To investigate the relationship between them, the spatial distribution characteristics of the disturbances are analysed, taking into account the influence of solar and geomagnetic activity on the disturbances; the variation characteristics of the disturbances in seismic and non-seismic regions are compared; the numbers of the disturbances before and after earthquakes are statistically analysed; and the statistical results of different earthquake groups are verified by comparison with random events. Finally, according to these analysis results, it can be concluded that most of the disturbances are related to ionospheric activities; some of disturbances are indeed related to seismic activity; the disturbances caused by seismic activities usually appear before the earthquakes. In terms of standardized probability, the results for M ≥ 6 earthquakes and sea earthquakes are most significant, exceeding two times the standard deviation at least 10 and 25 days before the earthquake, while the results for deep earthquakes (D ≥ 60 km) and land earthquakes are not significant. However, the disturbances caused by seismic activities are very weak and are hidden in those strong ionospheric activities. Therefore, the seismic ionospheric phenomena are so difficult to extract and identify, and more caution should be taken in the identification in future seismo-ionospheric phenomena research.

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