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

Abstract

. 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.

Temporal and spatial analyses on seismo-electric anomalies associated with the 27 February 2010 <i>M</i> = 8.8 Chile earthquake observed by DEMETER satellite

“…Although it is not statistically significant, the whistlers tend to reduce over the epicenter (Figs. 1, 2, and 4; Table 1), which generally agrees with Liu et al (2013). Anagnostopoulos and Papandreou (2012) reported possible links between space condition and large earthquakes.…”

“…Thus, the seismo-N e anomalies in the vast area could be contaminated by the Weddell Sea anomaly. Liu et al (2013) statistically studied low-latitude whistlers and 20 M = 5.0 earthquakes in Taiwan, and found the whistlers around the epicenters significantly decrease before the earthquakes. They suggested that whistlers depart from the earthquake preparation area, which results in whistlers significantly decreasing around the epicenter.…”

Identification of Very Low Frequency (VLF) Whistlers transients using Feed Forward Neural Network (FFNN)

“…The accurate spectral analysis of whistlers enables us to study the behavior of electromagnetic emissions and their propagation in ionosphere and magnetosphere. From the last few decades whistlers transient have also been used as earthquake precursor [7], therefore, proper accurate identification of whistlers is very important. Whistlers are difficult to detect because of their short duration.…”

Reply to comment by F. Masci and J. N. Thomas on “Temporal and spatial precursors in ionospheric total electron content of the 16 October 1999 Mw7.1 Hector Mine earthquake”

“…It has been known that the ionosphere can be disturbed by solar flares [ Liu et al ., , ], magnetic storms [ Liu et al ., , , , ; Lee et al ., , ; Lin et al ., , , , , ; Chen and Liu , ; Chuo et al ., ; Li et al ., , ; Huang et al ., ; Balan et al ., , , ; Lekshmi et al ., ; Sun et al ., ], eclipses [ Yeh et al ., ; Huang et al ., ; Liu et al ., , ; Tsai and Liu , ; Lin et al ., ], atmospheric tides [ Lin et al ., ], earthquakes [ Liu et al ., , , , , , , , , , , ], tsunami [ Liu et al ., ; Tsai et al ., ; Kakinami et al ., ], etc. The median base analysis has been employed to detect anomalies possibly related to earthquakes [ Liu et al ., , , ] and disturbances triggered by magnetic storms [ Liu et al ., ] in temporal variations of ionospheric critical frequency f o F 2 and/or GPS TEC (total electron content).…”