Ionospheric N e disturbances before 2007 Pu’er, Yunnan, China, earthquake

Selecting three half orbits near the epicenter of Pu’er earthquake, we analyzed the N e data recorded in their revisited orbits during a year before this earthquake, and extracted N e precursors. The results show that: ① There are significant seasonal variations of ionospheric N e in night time, which exhibit different shapes respectively in four seasons; ② There are three main shapes of N e : single-peak, saddle-shaped and even-shaped, all of which may occur in four seasons, but each season with its typical shape relatively; ③ Spatial images of N e showed high values near the epicenter in 30 days before the earthquake, and there is a good correlation between anomaly and distribution of earthquake in space and time, which reflects that these spatial anomalies were indeed concerned with the earthquake; ④ There shows a certain similarity of the N e curves among revisited orbits, which can provide background information for distinguishing and identification of seismic anomaly.