In this study, a TEC variation window value was selected based on the wavelet power spectrum method to analyze the seismic–ionospheric coupling relationship. In the full-time domain, a 27-day periodicity of the wavelet power spectrum was obtained that passed the 95% significance test. The sliding interquartile range method was used to analyze earthquakes above Mw6.5 in Japan from 2011 to 2022, excluding the hybrid effects between earthquakes close to one another. The sunspot number (SSN), 10.7 cm radio flux (F10.7), total solar irradiance (TSI), solar wind velocity (Vsw), geomagnetic activity index in the equatorial region (DST), and global geomagnetic activity index (KP) were used as indices representing solar and geomagnetic activity. After removing solar and geomagnetic interference from ionospheric anomaly changes using the sliding interquartile range method, the TEC anomaly changes before the earthquake were verified as being caused by the earthquake and analyzed. The statistical analysis of ionospheric total electron content (TEC) anomalies showed that earthquake magnitude was positively correlated with the amplitude of TEC anomalies but not linearly. The occurrence time of ionospheric anomalies lagged behind to some extent with the increase in earthquake magnitude. Additionally, abnormal changes on the 29th day (15 February 2022) before the 20th earthquake did not conform to previous research rules. According to the lithosphere–atmosphere–ionospheric coupling (LAIC) mechanism and global ionospheric map (GIM) studies, the TEC anomaly was consistent with the vertical projection of the epicenter with obvious regularity. The results show that these TEC anomalies may be related to earthquakes.

In order to study the seismic-ionospheric coupling relationship, this paper selects window values based on wavelet power spectrum method, and obtains the 27-day periodicity of wavelet power spectrum in the full time domain that passes 95% significance test. Then, sliding quartile method is used to analyze the earthquakes above Mw6.5 in Japan from 2011 to 2022, which exclude hybrid effects. Sunspot number (SSN), 10.7cm radio flux (F10.7), solar wind velocity (Vsw), storm ring current index (DST), and global Geomagnetic activity index (KP) are excluded as interference terms to eliminate the influence of solar and geomagnetic activity. According to the lithosphere-atmosphere-ionospheric coupling mechanism (LAIC) and global TECmap, the abnormal changes on the 29th day before the earthquake (February 15, 2022), which do not conform to the previous research rules, are analyzed to prove that TEC anomalies caused by earthquakes. The statistical analysis of ionospheric TEC anomalies shows that the magnitude of earthquake is positively correlated with the amplitude of TEC anomalies, and the occurrence time of ionospheric anomalies tends to lag as the magnitude increases.