Phenomena of electrostatic perturbations before strong earthquakes (2005–2010) observed on DEMETER

X Zhang (1) , X Shen (1) , Michel Parrot (2) , Z Zeren (1) , X Ouyang (1) , J. Liu (1) , J Qian (1) , S Zhao (1) , Y Miao (1)

1 Institute of Earthquake Science, CEA, Beijing
2 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

During the DEMETER operating period in 2004– 2010, many strong earthquakes took place in the world. 69 strong earthquakes with a magnitude above 7.0 during January 2005 to February 2010 were collected and analysed. The orbits, recorded in local nighttime by satellite, were chosen by a distance of 2000 km to the epicentres during the 9 days around these earthquakes, with 7 days before and 1 day after. The anomaly is defined when the disturbances in the electric field PSD increased to at least 1 order of magnitude relative to the normal median level about 10 −2 µV 2 /m 2 /Hz at 19.5–250 Hz frequency band, and the starting point of perturbations not exceeding 10 • relative to the epicentral latitude. Among the 69 earthquakes, it is shown that electrostatic perturbations were detected at ULF-ultra low frequency and ELF-extremely low frequency band before the 32 earthquakes, nearly 46 %. Furthermore, we extended the searching scale of these perturbations to the globe, and it can be found that before some earthquakes, the electrostatic anomalies were distributed in a much larger area a few days before, and then they concentrated to the closest orbit when the earthquake would happen one day or a few hours later, which reflects the spatial developing feature during the seismic preparation process. The results in this paper contribute to a better description of the electromagnetic (EM) disturbances at an altitude of 660– 710 km in the ionosphere that can help towards a further understanding of the lithosphere-atmosphere-ionosphere (LAI) coupling mechanism.

Domaines: Planète et Univers [physics]

X Zhang, X Shen, Michel Parrot, Z Zeren, X Ouyang, et al.. Phenomena of electrostatic perturbations before strong earthquakes (2005–2010) observed on DEMETER. Natural Hazards and Earth System Sciences, 2012, 12, pp.75-83. ⟨10.5194/nhess-12-75-2012⟩. ⟨insu-01179988⟩