Abstract: In this paper, we focused on the characteristics of the seismo-ionospheric effects related to the 2021 M_S7.4 earthquakes in Maduo, Qinghai, China, which were detected by the China Seismo-Electromagnetic Satellite (ZH-1 satellite). By applying the sliding interquartile range method and the wavelet transform method to electron density (N_e) data acquired by the Langmuir probe (LAP) and ion density (N_i) data, including He⁺ and O⁺ data, acquired by the plasma analyzer package (PAP) onboard the ZH-1 satellite, synchronous anomalies of N_e, He⁺ and O⁺ were found under quiet geomagnetic conditions on 14 May and 16 May 2021—that is, 7 d and 5 d before the earthquakes, respectively. In addition, based on multiple evidence relating to earthquake precursor anomalies, we can divide that three preparation processes of the 2021 M_S7.4 Maduo earthquake, including early period of stress expansion, late period of stress expansion and acceleration period of impending earthquake, and we can conclude that it is possible that this earthquake affected the ionosphere through the acoustic, and electromagnetic channels, as described by the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model.

Key words: ZH-1 satellite, Seismo-ionospheric effects, Electron density, Ion density, Sphere-coupling mechanism