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The intensity decrease of VLF electromagnetic waves around 1.7 kHz observed by DEMETER satellite within 4 hours before 4.8 mainshock of global earthquakes (EQs) within 550 km epicentral distance (537 earthquakes in total) was statistically found by Němec et al. [Geophys. Res. Lett., 2008; J. Geophys. Res.. 2009] and Píša et al. [J. Geophys. Res., 2013]. Our analysis also showed that the statistical comparison between the whistler wave data observed by the DEMETER and the lightning location data provided by World-Wide Lightning Location Network (WWLLN), we found that the intensity decrease was caused by not only change of earth-ionosphere cut-off frequency (i.e., approximately 1.7 kHz) but also absorption of whistler waves due to D-region electron density increase. In addition, we found the statistical correlation between the intensity decrease and EQ occurrences. Thus, one can expect that an in-situ monitoring of VLF electromagnetic waves on the satellite will provide the EQ prediction. In particular, the intensive whistler wave can be observed by nano-satellite, which also provides the practical precursor monitoring for the EQ prediction.