Analysis of ionospheric anomalies before earthquakes with Mw6.5 and above in Japan during 2011-2022

Abstract

Abstract 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.