HR: 11:20h
AN: S42B-05 [Abstracts]
TI: Observations of Electromagnetic Perturbations Shortly Before Earthquakes Onboard a Low-Orbiting Spacecraft
AU: * Nemec, F
EM: frantisek.nemec@gmail.com
AF: LPCE/CNRS, 3A Avenue de la Recherche Scientifique, Orleans, 45071, France
AU: * Nemec, F
EM: frantisek.nemec@gmail.com
AF: Charles University, V Holesovickach 2, Prague, 18000, Czech Republic
AU: * Nemec, F
EM: frantisek.nemec@gmail.com
AF: IAP ASCR, Bocni II 1401, Prague, 14131, Czech Republic
AU: Santolik, O
EM: ondrej.santolik@mff.cuni.cz
AF: Charles University, V Holesovickach 2, Prague, 18000, Czech Republic
AU: Santolik, O
EM: ondrej.santolik@mff.cuni.cz
AF: IAP ASCR, Bocni II 1401, Prague, 14131, Czech Republic
AU: Parrot, M
EM: mparrot@cnrs-orleans.fr
AF: LPCE/CNRS, 3A Avenue de la Recherche Scientifique, Orleans, 45071, France
AU: Berthelier, J
EM: jean-jacques.berthelier@cetp.ipsl.fr
AF: CETP/CNRS, 4 Avenue de Neptune, SaintMaur des Fosses, 94107, France
AB:
We present a statistical study of intensity of VLF (up to 10 kHz)
electromagnetic waves in the top side ionosphere above the earthquakes. More than 2.5
years of data recorded by the French micro-satellite DEMETER (altitude of orbit 700 km)
and a specially developed two-step data processing method have been used.
In the first step, a map of electromagnetic emissions that contains a statistical
description of wave intensity at a given point of the satellite orbit under given
conditions is constructed. In the second step, the wave intensity close to earthquakes
is evaluated. Changes of wave intensity related to the seismic activity are
investigated and their statistical significance is analyzed.
Earthquakes with magnitude larger than 4.8 that occurred all over the world during
the analyzed period (~ 9000 earthquakes) have been included in the study. It is shown
that the observed intensity of electromagnetic waves decreases during the night
by 4-6 dB shortly before earthquakes (up to 4 hours before the time of the main
shock). Spatial scale of the affected area is approximately 300 km. A possible
explanation of the observed effects is suggested.
UR: http://os.matfyz.cz/papers/agu2007/
DE: 2487 Wave propagation (0689, 3285, 4275, 4455, 6934)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting