A statistical study on ELF-whistlers/emissions and M ≥ 5.0 earthquakes in Taiwan

In this paper, we conduct statistical approaches to study the potential relation between ELF-whistlers/emissions below 100 Hz and 20 M ≥ 5.0 earthquakes occurred in Taiwan in the period from 26 August 2003 to 13 July 2004. Occurrence ratios of the ELF-whistler and ELF-emission of the entire study period are computed as the reference backgrounds. Our study shows that the ELF-whistlers and ELF-emissions during the earthquake period appear less and more frequently than their associated backgrounds, respectively. For the ELF-emission, the larger earthquakes generally yield the higher occurrence ratios. The statistical analyses confirm that the occurrence ratios of the ELF-emission significantly enhance 5-7 days before the earthquakes and are proportional to the earthquake magnitude but inversely to the distance from the observatory to the epicenter. Key Points The ELF-emissions significantly enhance before large earthquakes The appearance of the ELF-emissions is proportional to the earthquake magnitude Less chance observing the ELF-emissions if far away from the epicenter