Decrease of intensity of ELF/VLF waves observed in the upper ionosphere close to earthquakes: A statistical study

0330763 - ÚFA 2010 RIV US eng J - Journal Article
Němec, František - Santolík, Ondřej - Parrot, M.
Decrease of intensity of ELF/VLF waves observed in the upper ionosphere close to earthquakes: A statistical study.
[Pokles intenzity nízkofrekvenčních vln pozorovaných ve vrchní ionosféře v blízkosti zemětřesení: statistická studie.]
Journal of Geophysical Research. Roč. 114, - (2009), A04303/1-A04303/10. ISSN 0148-0227
R&D Projects: GA ČR GA205/06/1267
Institutional research plan: CEZ:AV0Z30420517
Keywords : DEMETER * seismo-electromagnetic effects * earthquake prediction
Subject RIV: BL - Plasma and Gas Discharge Physics
Impact factor: 3.082, year: 2009

We present results of a systematic study of intensity of VLF electromagnetic waves observed by the DEMETER spacecraft in the upper ionosphere (altitude 700 km). We focus on the detailed analysis of the previously reported decrease of wave intensity shortly before the main shock during the nighttime. Using a larger set of data (more than 3.5 years of measurements) and a newly developed data processing method, we confirm the existence of a very small but statistically significant decrease of wave intensity 0–4 hours before the time of the main shock at frequencies of about 1.7 kHz. It is shown that the decrease does not occur directly above the earthquake epicenter but is shifted about 2 degrees in the westward direction. Moreover, it is demonstrated that the decrease occurs more often close to shallower earthquakes and close to earthquakes with larger magnitudes, as it is "intuitively" expected, representing an additional proof of validity of the obtained results.

Statistická studie intenzity elektromagnetických vln pozorovaných družicí DEMETER v blízkosti zemětřesení.
Permanent Link: http://hdl.handle.net/11104/0176475