## 5 Conclusions  
In this paper, the global RO profiles from the FORMOSAT-3/COSMIC system were used to construct global maps of the ionosphere electron density 15 days before Chile's Concepcion earthquake (27 February 2010). By kriging interpolation, the disturbances of the Nmf2 parameter and the ionosphere's structure at different heights in the 15 days before the earthquake were compared and analyzed. The results show a noticeable disturbance in the F2 layer near the epicenter on February 21 and 25, and the abnormal area had an apparent local effect. Compared with other periods, the maximum disturbing momentum of Nmf2 over the epicenter of the two days was more than 50%. The ionosphere anomaly had an absolute directional difference. The disturbance peak point appeared in the north of the epicenter on February 25, with the disturbance point occurring in the southeast of the epicenter on February 21. Simultaneously, the electronic density profiles at these COSMIC occultation points were detected to have irregular oscillations below the F layer. The difference in the vertical structure of the ionosphere resulted in different responses to earthquakes at separate heights. The local effect was the most obvious between 200 and 300 km. The ionosphere disturbance at a height over 400 km gradually weakened. Influenced by the neutral atmosphere, the ionosphere in the bottom layer presented an irregular disturbance. Jointed by the similar response of GIM TEC, the traveling ionospheric disturbance was confirmed to appear across the bottom to the upper layer. These phenomena proved the possibility of the multi-channel coupling effect of the seismo-ionosphere. **Supplementary Materials:** The following are available online at [[https://www.mdpicom/article/10.3390/rs13142724/s1](https://www.mdpicom/article/10.3390/rs13142724/s1)]([https://www.mdpicom/article/10.3390/rs13142724/s1](https://www.mdpicom/article/10.3390/rs13142724/s1)), Figure S1: COSMIC occultation distribution on UTC 12-14 h, 12 February 2010 (15 th day before shock), Figure S2: COSMIC RO spatial distribution under (a) earth-fixed coordinate system and (b) geomagnetic-sun-fixed coordinate system to reflect the F-layer variations. **Author Contributions:** Conceptualization, writing and funding acquisition, K.S. and J.G. ; investigation, validation, Y.Z. and W.L. ; methodology and resources, Q.K. ; software and formal analysis, T.Y. All authors have read and agreed to the published version of the manuscript. **Funding:** This research is supported by the National Natural Science Foundation of China, grant No. 41774001 and 41704015; the Autonomous and Controllable Special Project for Surveying and Mapping of China, grant No. 816-517; the SDUST Research Fund, grant No, 2014 TDJH101; the Natural Science Foundation of Suqian, grant No. K201914; and the Open Research Fund Program of the Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, China, grant No. 20-02-05. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The COSMIC Radio Occultation data used in the paper can be downloaded from [[http://tacc.cwb.gov.tw/](http://tacc.cwb.gov.tw/)]([http://tacc.cwb.gov.tw/](http://tacc.cwb.gov.tw/)) or [[http://cdaac-www.cosmic.ucar.edu/cdaac/](http://cdaac-www.cosmic.ucar.edu/cdaac/)]([http://cdaac-www.cosmic.ucar.edu/cdaac/](http://cdaac-www.cosmic.ucar.edu/cdaac/)) (accessed on 1 June 2021). The GIM TECs for result validations are accessed by [[ftp://cddis.gsfc.nasa.gov/gnss/products/ionex/](ftp://cddis.gsfc.nasa.gov/gnss/products/ionex/)]([ftp://cddis.gsfc.nasa.gov/gnss/products/ionex/](ftp://cddis.gsfc.nasa.gov/gnss/products/ionex/)) (accessed on 1 June 2021).