Abstract
The aim of this study is to check if there is a relationship between the seismic activity and the whistlers observed by the micro-satellite DEMETER. Whistlers are the waves emitted by lightning strokes during thunderstorm activity. They use to propagate in the Earth-ionosphere waveguide but also in the ionosphere and the magnetosphere mainly along the magnetic field lines. Due to this reason we have checked the whistler occurrence not close to earthquake epicenters but close to the magnetically conjugate point of these epicenters at the satellite altitude. The number of whistlers is given by a neural network in operation onboard the satellite. It appears that the whistler amplitude is attenuated at the satellite altitude around the magnetic equator. It is why we have removed the earthquakes occurring at low geomagnetic latitudes in the statistic. The whistler rate is normalized with a background value to take into account the seasons and the epicenter locations. A superposed epoch method is used to display the results between -15 and +5 days around the earthquake day and up to 1000 km from the conjugate point of the epicenters. It is shown that the whistler rate is higher the day before the earthquake at a distance less than 200 km. It would be unrealistic to believe in the possibility to use this study for earthquake prediction because everyday thunderstorm activity reliably masks seismic effects. But it is further evidence that there is a lithosphere-atmosphere-ionosphere coupling at the time of the seismic activity.
Highlights
The possible relation between thunderstorm activity and seismic activity is an old question
A sferic is the wave emitted by a lightning stroke which propagates in the Earth-ionosphere waveguide
One can see that the whistler rate increases by 11% at less than 200 km from the Epicenter Conjugate point (ECP) and one day before earthquakes with M ≥ 5.5 and d ≤ 20 km
Summary
The possible relation between thunderstorm activity and seismic activity is an old question. Concerning the M7.2 Hyogoken-Nanbu earthquake of January 17, 1995 in Japan, strong lightning discharges have been detected in association with intense radio noises one week prior to the main shock [8] [9]. It has been noticed an increase in the amplitude of lightning electromagnetic signals (atmospherics) received at Yakutsk, 12 - 14 days before the M9 Tohoku earthquake in Japan [10]. A more global analysis has been done in [13] [14] close to Taiwan They have performed a statistical correlation between lightning activities and M ≥ 5.0 earthquakes occurring during 1993-2004. Note that our study is not related to earthquake lights (see for example [15] [16] [17]) because these lights are faint and diffuse and correspond to a very different phenomenon
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