## 1 Introduction  
An earthquake (EQ) is one of the most destructive natural disasters, and discerning seismic precursors has been one of the most challenging topics for scientists in the last ion density detected by the DEMETER satellite before the Ms 7.9 Tonga Islands EQ in 2006. [PERSON] et al. [13] analyzed the Bayan Mw 6.9 EQ, which occurred in 2018, using ground and satellite data, and they built a new lithospheric-atmospheric-ionospheric-magnetospheric coupling model to analyze the anomalous observations before and at the moment of the EQ occurrence. In recent years, the China Seismo-Electromagnetic Satellite (CSES-01), which is also called ZHANGHENG-1, was launched on 2 February 2018, on a sun-synchronous orbit at an altitude of \(\sim\)507 km with a high orbital inclination of 97.4\({}^{\circ}\) and a recursive period of 5 days. The ascending/descending node local time (LT) is fixed at 2:00/14:00, respectively. The main scientific objectives of CSES-01 are to detect the electromagnetic field/waves, ionospheric plasma, and charged particles intended to survey the space environment and the ionospheric disturbances that may be associated with destructive EQs, volcano explosions, tsunamis, and space weather anomalies, and to analyze the Lithosphere-Atmosphere-Ionosphere (LAI) coupling mechanism [14]. In addition, China and Italy are jointly building the second one, i.e., CSES-02, which will be launched in 2024. CSES-02 will also provide almost the same physical field parameters as CSES-01 but with numerous specific optimizations based on CSES-01's in-orbit performance. Using the CSES-01 data, the pre-EQ ionospheric anomalies have already been widely studied. [PERSON] et al. [15] statistically analyzed the seismo-ionospheric effects of electron density and oxygen ion density detected by the DEMETER and CSES-01 satellites. They suggested that the CSES-01 could effectively detect ionospheric disturbances during strong EQs, as the DEMETER satellite does. [PERSON] et al. [14] reported the simultaneous disturbances of ion drift velocity and oxygen ion density recorded by the orbit closest to the epicenter five days before the Venezuelan Ms 7.3 EQ in 2018. [PERSON] et al. [16] analyzed possible perturbations in the electric field detected by CSES-01 before the Mw 7.7 Caribbean Sea EQ occurred in 2020. [PERSON] et al. [17] reported the possible plasma disturbance characteristic before four shallow-focus EQs in Indonesia were detected by CSES-01 in 2018. More recently, [PERSON] et al. [18] put forward the routine data preprocessing and seismo-ionospheric information extraction methods by using CSES-01 data and other multi-source data and provided the results of the possible seismo-ionospheric anomalies that appeared during the Ms \(\geq\) 7 shallow EQs recorded by CSES-01. [PERSON] et al. [19] analyzed the seismo-ionospheric electron density disturbances observed by CSES-01 through a spatial analysis method. These new scientific research results bring hope for a breakthrough in EQ forecasting. However, due to the insufficient amount of experimental evidence supporting those theories, there are also some debates on the possibility of seismo-ionospheric precursors; thus, the existence of ionospheric perturbations before EQs is controversial [9; 13; 20]. One of the main challenges for seeking seismic precursors from the ionosphere is that strong EQ events happen so occasionally around the globe, and there is a large time period and space among them, so it is difficult to compare and summarize the regularity and relevance of EQ precursors. From August to October 2018, a series of strong EQ events occurred in southeast Asia and northern Oceania (22\({}^{\circ}\)S to 0\({}^{\circ}\)N, 115\({}^{\circ}\)E to 170\({}^{\circ}\)E), providing a rare opportunity for EQ precursor research.