Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 22, 4123-4131, 2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
22 Dec 2004
Variations of the ionospheric electron density during the Bhuj seismic event
A. Trigunait1, M. Parrot1, S. Pulinets2, and F. Li1 1Laboratoire de Physique et Chimie de l’Environnement, Centre National de la Recherche Scientifique, Orléans, France
2Instituto de Geofísica, UNAM, Ciudad Universitaria, Delegacíon de Coyoacán, 04510, México D.F., Mexico
Abstract. Ionospheric perturbations by natural geophysical activity, such as volcanic eruptions and earthquakes, have been studied since the great Alaskan earthquake in 1964. Measurements made from the ground show a variation of the critical frequency of the ionosphere layers before and after the shock. In this paper, we present an experimental investigation of the electron density variations around the time of the Bhuj earthquake in Gujarat, India. Several experiments have been used to survey the ionosphere. Measurements of fluctuations in the integrated electron density or TEC (Total Electron Content) between three satellites (TOPEX-POSEIDON, SPOT2, SPOT4) and the ground have been done using the DORIS beacons. TEC has been also evaluated from a ground-based station using GPS satellites, and finally, ionospheric data from a classical ionospheric sounder located close to the earthquake epicenter are utilized. Anomalous electron density variations are detected both in day and night times before the quake. The generation mechanism of these perturbations is explained by a modification of the electric field in the global electric circuit induced during the earthquake preparation.

Key words. Ionosphere (ionospheric disturbances) – Radio Science (ionospheric physics) – History of geophysics (seismology)

Citation: Trigunait, A., Parrot, M., Pulinets, S., and Li, F.: Variations of the ionospheric electron density during the Bhuj seismic event, Ann. Geophys., 22, 4123-4131,, 2004.
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