Response of the ionospheric electron density to different types of seismic events

Abstract

The electron density data recorded by the Langmuir Probe Instrument (ISL, Instrument Sonde de Langmuir) onboard the DEMETER satellite have been collected for nearly 4 yr (during 2006–2009) to perform a statistical analysis. During this time, more than 7000 earthquakes with a magnitude larger than or equal to 5.0 occurred all over the world. For the statistical studies, all these events have been divided into various categories on the basis of the seismic information, including Southern or Northern Hemisphere earthquakes, inland or sea earthquakes, earthquakes at different magnitude levels, earthquakes at different depth levels, isolated events and all events. To distinguish the pre-earthquake anomalies from the possible ionospheric anomalies related to the geomagnetic activity, the data were filtered with the <i>K<sub>p</sub></i> index. The statistical results obviously show that the electron density increases close to the epicentres both in the Northern and the Southern Hemisphere, but the position of the anomaly is slightly shifted to the north in the Northern Hemisphere and to the south in the Southern Hemisphere. The electron density related to both inland and sea earthquakes presents an anomaly approximately close to the epicentres, but the anomaly for sea earthquakes is more significant than for inland earthquakes. The intensity of the anomalies is enhanced when the magnitude increases and is reduced when the depth increases. A similar anomaly can also be seen in the statistical results concerning the isolated earthquakes. All these statistical results can help to better understand the preparation process of the earthquakes and their influence up to the ionospheric levels

Statistical Study on Variations of the Ionospheric Ion Density Observed by DEMETER and Related to Seismic Activities

“…The distance occurrence of the ionospheric perturbations before earthquakes is consistent with the statistical study by He et al (). In their analysis, the result shows that there are anomalies close to the epicenters prior to the occurrence of earthquakes.…”

Analysis of pre-earthquake ionospheric anomalies before the global <i>M</i> = 7.0+ earthquakes in 2010

“…Therefore, the anomaly may have been caused by other reasons. He et al (2011) and Le et al (2011) statistically studied pre-earthquake ionospheric anomalies using different methods. They found that anomalies occurring before deep focus earthquakes had smaller intensity and occurrence rates.…”

Recent progress in ionospheric earthquake precursor study in China: A brief review

“…Corresponding ionospheric effects were also observed in the magnetically conjugated region, but both the probability and amplitude are lower than those near the epicenter region. Based on electron density recorded by the DEMETER satellite during 2006, He et al (2011 also reported that the electron density increased close to the epicenters both in Northern and Southern Hemisphere. Moreover, they found that the intensity of the anomalies was enhanced when the magnitude increased and was reduced when the depth increased, which is consistent with the results of Le et al (2011).…”