Electron and ion density variations before strong earthquakes (<i>M</i>>6.0) using DEMETER and GPS data

Abstract

Abstract. Using IAP (plasma analyzer) and ISL (Langmuir probe) experiments onboard DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite and GPS (Global Positioning System) measurements, we have statistically analyzed the variations of the electron and ion densities to search for disturbances in the vicinity of four large earthquakes prior to events. The indices D st and K p were used to distinguish pre-earthquake anomalies from the other anomalies related to the geomagnetic activities. For each studied case, a very good agreement was found between the different parameters estimated by DEMETER and GPS data in the detection of pre-seismic anomalies. Our statistics results show that the anomalous deviations prior to earthquakes have different sign from case to case, and that their amplitude depends on the magnitude of the earthquake. It has also been found that the electron density measured by the ISL experiment at night detects anomalous variations significantly before the earthquakes. The appearance of positive and negative anomalies in both of DEMETER and TEC (Total Electron Content) data during 1 to 5 days before all studied earthquakes during quiet geomagnetic conditions indicates that these anomalous behaviors are highly regarded as seismo-ionospheric precursors.

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan <i>M</i><sub><i>S</i></sub> 8.0 earthquake

“…The strong seismotelluric current is thought to run mainly along the Longmenshan fault and electromagnetic oscillations, induced by the current and predominated by ULF frequency band, propagate up to the ionosphere and give rise to perturbations of ionospheric parameters. Some of these parameters have been investigated, such as GPS TEC and f0F2 (Yu et al, 2009;Xu et al, 2010;Akhoondzadeh et al, 2010), DEMETER satellite O+ density (Zhang et al, 2009b), electron density and electron temperature (Zeng et al, 2009), etc. Fortunately, all of these study results present a climax on 9 May 2008 and this indicates a LAIC or interaction aroused by these electromagnetic signals prior to the Wenchuan event.…”

Investigation of VLF and HF waves showing seismo-ionospheric anomalies induced by the 29 September 2009 Samoa earthquake (<i>M</i><sub>w</sub>=8.1)

“…The geomagnetic conditions are quiet on these dates (Kp<2.5 and Dst>−20 (nT)). A dominant anomaly was observed in electron density parameter measured by ISL (Langmuir probe) sensor, 5 days before the earthquake at nighttime (Akhoondzadeh et al, 2010). Using the analysis of the DEMETER data, Molchanov et al (2006) reported a drop of the VLF signals radiated by ground transmitters prior to large earthquakes.…”

“…The time series of the electron temperature variations, measured by the ISL experiment, display a sudden increase in electron temperature, 2 days before the earthquake, at ∼22:30 LT (Akhoondzadeh et al, 2010).…”

“…Recently we have observed seismo-ionospheric anomalies using DEMETER experiments and TEC (Total Electron Content) data during a recent (29 September 2009) major earthquake (M w =8.1) close to the Samoa Islands (Akhoondzadeh et al, 2010). In Sect.…”

“…There are two modes of operation: (i) a survey mode to record low bit rate data all around the Earth at invariant latitudes less than ∼65 • , and (ii) a burst mode to record high bit rate data above seismic regions. Parrot et al (2006b), Sarkar et al (2007) and Akhoondzadeh et al (2010) described examples of variation of plasma parameters recorded by DEMETER data over epicenters of some earthquakes before their occurrence. Moreover, pre seismic anomalies in the registered VLF transmitter signals by electromagnetic experiments of DEMETER have been already reported (Molchanov et al, 2006;Rozhnoi et al, 2007Rozhnoi et al, , 2008Slominska et al, 2009).…”