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Investigation of Ionospheric Anomalies Based on GPS Ionospheric Technology in Earthquakes

In our paper, we use ionospheric tomography technology, which was proposed by Austen et al. in 1986, to detect a three-dimensional map of ionosphere over the epicenters of different magnitude earthquakes in Japan, Sumatra, Taiwan and Xinjiang China. We use the anomaly detection method to detect the electron density anomies and analyze earthquake ionospheric anomaly statistics. It is concluded that: 1) There are distinct ionospheric abnormalities in a few days or a few hours before the earthquake, especially in the 1-2 days before the earthquake near the epicenter. The earthquake accounts for the anomalies, with the exception of effects from solar activity and terrestrial magnetic field. 2) The abnormal ionospheric electron density area is generally near the epicenter, with a small offset from the epicenter. The closer to the epicenter, the greater the ionospheric anomaly. 3)The convincing functional relationship between negative or positive anomalies and earthquakes is not found yet.